Investigators zero in on duck boat's axle in hunt for cause of crash that killed four students and injured dozens after 'vehicle's left tire locked up'
- Seattle duck boat crashed into tour bus on Aurora Bridge in Seattle on September 24
- Four international students from Austria, China, Indonesia and Japan were killed
- Over 40 people were rushed to hospital, where 15 remain
- Authorities say that duck boat's axle was sheared off but aren't sure if the damage was done before or after fatal collision
- 'The left front axle was sheared off - for what reason yet, we don't know' said National Transportation Safety Board Member Earl Weener
The left front axle of the amphibious duck boat involved in a deadly Seattle accident was sheared off, but federal investigators said Saturday they don't know if it was damaged before the collision with a charter bus that killed four international college students.
National Transportation Safety Board Member Earl Weener said the axle will be sent to a federal lab for further examination. It's too soon to know how the axle was damaged, Weener said.
Witnesses have said they saw the duck boat's left tire lock up Thursday as it swerved into a charter bus carrying international students over a bridge.
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A medical examiner checks the scene of a crash between a tour bus and a tourist duck boat on the Aurora Bridge in Seattle, Washington on September 24
An injured young woman is taken to a waiting ambulance at the scene of an accident between a duck boat and a tour bus in Seattle - four international students on the tour bus were killed - authorities are now investigating the duck boat's axle
Authorities investigate the horrific crash site between two tour vehicles loaded with tourists and students (above) - witnesses have said they saw the duck boat's left tire lock up before it swerved into the bus
Seattle Mayor Ed Murray (center) is escorted by firemen onto the deadly scene of a crash between a tour bus and a tourist duck boat that killed four students
'I saw a bunch of smoke and what appeared to be the front left wheel pop off, and then it clipped a smaller SUV and basically almost T-boned into the oncoming bus and spun around,' witness Jesse Christenson told NBC News.
Other witnesses said the duck boat seemed to lurch suddenly into oncoming traffic.
Four North Seattle College students from Austria, China, Indonesia and Japan were killed.
'The left front axle was sheared off - for what reason yet, we don't know,' Weener said at a news conference.
Weener said the axle and parts of the drive mechanism would be sent to the NTSB labs in the hope of understanding the characteristics of the fracture and whether it contributed to the crash, or whether it occurred before or after the crash, reported the outlet.
Weener added: 'It's way too early to say anything about a probable cause.'
Investigators are also examining the charter bus and two other vehicles involved in the accident - a pickup truck and an SUV.
Weener also said investigators would determine what the drivers of the duck boat and the charter bus were doing for the three days before the crash.
The federal probe is expected to take months, and Weener said 'it's way too early to say anything about a probable cause."
The investigation is being watched by other operators of the hugely popular duck boat tours.
Escape: A stunned woman with cuts on her face and her arm in a sling is taken into the back of an ambulance following the collision
Emergency workers walk the injured in stretchers to waiting ambulances following the fatal crash on September 24 on the Aurora Bridge in Seattle
Firefighters remove a body from the crushing wreck between a duck boat and a tour bus - four students died
'Safety and security are always a concern,' said Cindy Brown of Boston Duck Tours. 'When anything happens in our industry, we're all acutely aware.'
Brown said her operation hasn't changed any procedures, but the owners and safety team would evaluate the situation after the federal investigation is complete.
The amphibious vehicle tours are offered throughout the United States and the world, including in Philadelphia; Austin, Texas; Miami; Ft. Lauderdale; and London.
It's the first time the NTSB has looked into a land crash of the amphibious vehicles, which critics say are too dangerous for city streets.
The federal agency has scrutinized duck tour vehicles several times when they've been in accidents on water.
Federal investigators will spend a week or more on site.
State regulators also have opened an investigation, which entails inspecting all vehicle and driver records.
Duck boats, which can drive on land and in water, have been criticized by those who say they are dangerous traffic hazards - but the recent accident will be the first time a duck boat has been investigated by NTSB for an accident on land
A medical examiner checks the scene of the massive crash of a duck boat and tourist bus - 15 people remain hospitalized. The bus's front windows were blown out in the collision
A side view of the tour bus involved in the crash shows how the side of the vehicle was practically sheered right off by the duck boat - more than 40 people were injured
The amphibious vehicle involved in the crash - known as Duck No. 6 - underwent regular annual examinations by a federally certified inspector, most recently in 2015 and 2014, and met federal standards, Washington Utilities and Transportation Commission spokeswoman Amanda Maxwell said.
The state also reviews the company's fleet every few years, looking for systemic problems, Maxwell said. The last review, in December 2012, focused on a sample of the company's vehicles and did not include Duck No. 6.
'So far, our investigators are satisfied with the maintenance records' of the duck tours vehicle, Maxwell said.
Meanwhile, 15 people remain hospitalized at Harborview Medical Center, spokeswoman Susan Greggs said. One person remains in critical condition, eight are in serious condition and six in satisfactory condition, she said.
A sign at North Seattle Community College mourns the violent deaths of four of its international students, who were killed in the duck boat collision
Barb Graff, Seattle's director of the Office Emergency Management, said a private location has been established for families of the deceased and injured, where city, county and Red Cross workers are offering assistance and mental health counseling.
Several hotels in Seattle are making rooms available to the families free of charge, Graff said, and Delta and Alaska airlines are helping with flights.
'We're doing everything we can to help families make it through the tough time,' Graff said.
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