A separate accident, which happened around the same time on a nearby road, left one teen dead and a second in critical condition after their car struck a semitrailer truck. The two were headed to Cedar Grove High School.
Crews worked to clear I-43 of wreckage - identifying bodies and vehicles amid the tangled metal - into the night. The accident took place in Sheboygan County, just north of the Ozaukee County line, about 35 miles north of Milwaukee.
Authorities believe the accident, which was reported at 7:19 a.m., happened as cars in the southbound lanes began to strike each other as some slowed down in a dense fog.
As vehicles tried to get off the highway, more cars and trucks became involved, leading to a chain reaction - some witnesses reported hearing a horrific "bang, bang, bang" - that left a scene of carnage. An inferno raged, fueled by diesel fuel and a semitrailer truck loaded with paper products.
Witnesses said cars may have plunged into the pileup for up to five minutes.
"They were dealing with zero visibility," said State Patrol Sgt. John Jones. "Witnesses said cars just kept driving into the fog at a high rate of speed."
"In my 21 years, this is the most horrific scene I have ever seen," said Sheboygan County Sheriff Loni Koenig.
Officials said four other accidents occurred at nearby points of the highway, in both northbound and southbound lanes, including one in which a car rear-ended a semitrailer truck, ending up underneath it. All involved in those accidents survived.
Northbound lanes of I-43 were reopened Friday evening. Southbound lanes were expected to be open by this morning, assuming the damaged roadway could be repaired.
As night fell, floodlights were put in place so workers could continue removing the wreckage, even as traffic streamed along in the reopened northbound lanes. Firetrucks also were put in position, their headlights shining on the area.
Workers stood holding brightly colored tarps as others worked to remove the bodies, which were carried from the scene in numbered body bags. All the bodies were removed by 7:15 p.m.
Workers continued to remove mangled cars and trucks late into the night. One of the last vehicles left was a dump truck, its rear tires melted onto the roadway.
Dozens of gawkers - adults, high school students and even a couple with a small child - had parked along a side road and hiked a ways to watch the workers.
Trying to sort it out
Authorities were still trying to sort out the sequence of events late Friday, with seven to eight accident investigators on the scene for a tricky reconstruction effort that may resemble those after plane crashes.
Officials say they may have to use DNA to identify some of the victims, because bodies were burned severely in the fires and explosions. All of the victims died in their cars. One vehicle had two occupants, and the rest of those killed were sole occupants of their vehicles, said Jones of the State Patrol.
No children were among the victims, he added.
The names of the victims were not released because authorities were in the process Friday night of notifying the families of those killed.
Of the 36 injured, seven were in critical condition and one in serious condition at area hospitals. Some 28, whom officials referred to as the "walking wounded," were treated and released. Injuries ranged from burns to broken bones.
Groups of families, worried when loved ones did not make it home or to work as expected, began arriving early at the site, where firefighters were hosing down the wreckage and blue tarps were placed over vehicles in which bodies had been found. The tarps presented a startling contrast to the smoldering black and gray of the scene.
"I don't know how we got out of the car," said Patrick Parise, 24, of Green Bay, who was treated at Sheboygan Memorial Hospital.
He was traveling with his girlfriend, April Busse, also 24, and his little sister, Daniele Borchert, 8. The trio were on their way to Germantown to pick up Parise's other sister, Tara Tsay, 21, for a trip to Fort Lauderdale, Fla., for their grandfather's 80th birthday.
"April was driving the car, and I was sitting on the passenger side sleeping," Parise said. "Just before the accident, I heard April scream, 'Oh my God.' "
"I think we hit the pile, but I don't really know," he said. "I don't know how Daniele got out of the car, or how April got out. All I know is all of a sudden we were walking up the hill on the side of the freeway and there were all kinds of emergency medical people around us."
The accident was the deadliest in state history.
In March 1999, a van carrying a magazine sales crew overturned on I-90 near Janesville, killing seven. In February 1997, eight businessmen on an annual fishing trip were killed when their van was struck by a semitrailer truck on Highway 41 north of Slinger.
In 1937 in Manitowoc County, according to state records, nine people were killed when a family headed to Door County for a Memorial Day vacation collided with a car carrying three local men along what is now I-43. Only a small child survived the crash.
Heavy fog was identified as the main cause of Friday's accident, along with vehicles traveling too fast for conditions.
"It was a complete whiteout," said Larry Freitag, a truck driver for Piggly Wiggly who saw the accident unfold in front of him.
Freitag said he saw the boom of a Cablevision truck flip into the air. He later saw the burned wreckage of that truck. Another truck, a vehicle from Short Transportation, was burning when Freitag tried to rescue the driver. He couldn't get close.
"Flames shot out and I had to back off," he said. He never saw anyone emerge from the truck, he said.
Nathan Huenink, 22, of Sheboygan Falls said he was heading south on I-43 on a motorcycle. "You couldn't see 15 feet in front of you. All of a sudden, the car in front of me, the brake lights went on and I screeched to a stop. "
Huenink, whose birthday was Friday, said he darted around the car in front of him, only to hear another car slam into that one. "I could have been squished," he said, "It all happened in a split second."
"I pulled in front of a big truck because I knew that one wouldn't move if it got hit. I just hid out."
Huenink said he then heard a series of explosions. "There was just this black smoke billowing and billowing. . . . You felt almost like you were dreaming, that it couldn't be real. And you could hear cars screeching in behind you."
Seth Schwochert, a driver for Sheboygan Beverage, said he passed people standing by the highway - a big mistake, he thought. Other drivers, though, said people waving caused them to slow down.
Schwochert said he saw the fire from the crash first, and heard "bang, bang, bang," presumably more cars adding to the pile of twisted metal. At the same time, there were more crashes behind him and explosions in front.
Mike Hausmer, a drywall installer driving from Sheboygan to a job in Jackson, stopped his car to avoid hitting people who were pleading for help. He heard crashes behind him as he stopped, but decided not to get out of his vehicle.
"I felt better off staying in the truck," he said.
The accident occurred at an otherwise unremarkable point of the highway, near mile marker 113, a spot passed each day by some 24,000 vehicles. On I-43 between Milwaukee and Green Bay, the point near Cedar Grove is where the highway passes closest to Lake Michigan, which can contribute to foggy conditions.
As dozens of emergency workers - sheriff's deputies, state troopers, firefighters, ambulance crews - raced to the scene, officials closed an eight-mile stretch of I-43, from Highway 32 on the south to County Road D on the north.
And when the fog lifted and the TV helicopters finally brought the scene into focus, it was unlike many other chain-reaction pileups, in which a series of cars ends up angled domino-like across lanes and in ditches.
Instead, it appeared more like a bomb had exploded amid the farms and fields. Or as if the cars and trucks had been dropped from the sky, one on top of the next, with a horrible twist of blackened metal in the center and intact cars and trucks splayed across the highway at the edges.
There were some skid marks on the pavement, along with personal belongings - bags, empty soda bottles, a shoe. Some of the nearby grass had been charred.
The scene indicated that drivers had little, if any, warning that there were problems ahead, no sign of the fire and smoke inside the fog.
"I could see a little beyond this," said Jim Lawson, a truck driver with Jelco Transportation in Manhattan, Ill., patting the hood ornament on his truck.
"This is a bad stretch for fog, anywhere along the lake here," said Sherry Mulloy, who works at the nearby How-Dea Service truck stop in Belgium.
On foggy mornings, when she arrives for work, Mulloy said she often sees extra trucks in the parking lot, as nervous drivers get off the highway, but she did not notice more than normal Friday.
As word of the accident spread, nearby farmers and residents walked across fields of corn and alfalfa to get a glimpse of the scene, many leaning against a barbed-wire fence.
Even after the smoke dissipated, its smell lingered in the crisp fall air, an acrid odor with a tinge of chemicals.
Rows of firetrucks, ambulances and emergency vehicles lined the sides of the highway's northbound lanes, where some vehicles had been involved in separate accidents. Once the highway was shut down, emergency vehicles - including some from Saukville, Newburg, Random Lake and other towns - drove in from the opposite direction.
Worried family members
Some worried family members, searching for relatives, climbed a hill overlooking the freeway to survey the tangled mass of vehicles some 200 yards away.
Garwood Staggs of Sheboygan came looking for his cousin, Laurie Sorrel, 32, of Cairo, Ill., who was visiting relatives and left for home from Sheboygan, about 19 miles north of the crash site, at 7 a.m. Friday.
"I'm hoping she made it through before the accident," he said, his voice choked with emotion. "She doesn't have a cell phone. I don't know. I can't find her."
Others ventured closer, to within 40 feet of the main accident site, an exceedingly grim scene.
Area hospitals were flooded with calls from people checking to see if loved ones were on their injured list.
"Can you slow down and spell out the name?" asked Inga Von Appen, at the reception desk of the emergency room at Columbia St. Mary's Hospital, Ozaukee Campus, in Mequon.
By 11:20 a.m., when that call came in, she had already called to get a faxed list of patients at the other hospitals.
"I'm not understanding you," said Von Appen, reviewing the lists. "No, he is not at our hospital and he is not at Saint Nick's or Sheboygan Memorial."
Priests and pastors had already begun to mill about the waiting area, talking with families and victims, offering counseling and consolation.
Pastor Will Reichmann took a walk early Friday morning, a day he hadn't planned to work, and after seeing the news on television went to the hospital.
He spoke with two teenagers who survived the crash, who soon also were being comforted by their families.
"Some are still in a state of shock, said Reichmann, pastor of care and counseling at First Immanuel Lutheran Church in Cedarburg. "They find themselves not only traumatized by the accident but the trauma around them."
"For all of us, I think it makes us think not only of being careful but also to be ready, in case of an accident, to be ready to meet the Lord," said the Rev. Earl Slotman, pastor of Faith Reformed Church of Cedar Grove, who came to the scene looking for parishioners needing help.
He said a man who attends his church narrowly escaped the accident: "He was so close up that he smelled of smoke when he came home."
Bill O'Rourke of Sheboygan, a postal worker who travels I-43 daily to his job in Milwaukee, said the area where the accident occurred was often perilous for drivers because of dense fog.
He travels from his home to Milwaukee in 45 minutes when conditions are good, but the trip takes two hours when fog limits visibility.
"Maybe now they'll put up a sign saying, 'Entering dense fog area,' " O'Rourke said.
Contributors to this report were Dan Benson, Peter Maller, Jeff Cole and Lauria Lynch-German in Sheboygan County; Linda Spice in Ozaukee County; and Greg Borowski, Jessica Hansen, Jesse Garza, Annysa Johnson, Kelly Wells and Marilynn Marchione in Milwaukee.
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