Six people have died from the collapse of a newly installed pedestrian bridge on Florida International University's Miami campus, police said.

Five people were pronounced dead at the scene and another died after being transported to a hospital, Alvaro Zabaleta, a spokesman for the Miami-Dade Police Department, said at an early-morning press conference.

"There is the sad possibility that under the concrete there may be additional vehicles," Zabaleta said. "The engineers are working at it in a very tactical way. The structure is fragile and could be dangerous to rescue personnel."

Joe Raedle/Getty Images

Joe Raedle/Getty Images

Joining local authorities on the scene were officials from the National Transportation Safety Board and FBI. Engineering crews have worked nonstop, Zabaleta said.

"We've been working throughout the entire night," he said. "This is a very slow process. They're still working away at that concrete."

Late Thursday night authorities reclassified the mission to a recovery effort from a rescue effort, indicating it's unlikely survivors would be discovered in the wreckage.

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Roberto Koltun/The Miami Herald via AP

In addition to ensuring the safety of those digging through the rubble, efforts are slowed because there's probably evidence to be collected from what's left, Zabaleta said.

"We don't want to rush it and damage any evidence," he added. "That bridge, whatever's left of it, is very, very unstable."

The newly installed bridge, hailed as an engineering marvel, slammed to the ground around 1:30 p.m. on Thursday and immediately trapped at least eight vehicles, authorities said.

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Ten injured in the collapse were transported to Kendall Medical and labeled as level-one trauma patients, Dr. Mark McKenney, the hospital's program director, said on Thursday. They ranged in age from 20 to 50. Eight others were admitted with broken bones, bruises and abrasions. Additional patients may have been admitted to other facilities.

The NTSB is planning to investigate the collapse and plans to deploy a team of 15 specialists that includes engineering, material-science and survival-factor experts.

FIU touted the bridge to be one of the first of its kind, tweeting that it swung into place on Saturday.

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Florida Senator Marco Rubio, who described the incident as "troubling and tragic," said the bridge was constructed for safety after a student died last year crossing that intersection.

One woman who barely avoided the deadly collapse said she saw the structure crumble "in front of me, and it fell on the cars that were waiting for the light to change."

"I was near the light. I was the first car that moved forward when it changed and I was near the bridge. It was fine, and all of a sudden, I saw it collapse from the left towards the middle," Suzy Bermudez told media outlets including ABC News on Thursday.

"It was in slow motion," she said. "I didn’t hear anything -- my car windows were up and I had the radio on. But when I saw it happen, I jumped out of my car."

"I couldn't process it until I actually jumped out of my car," Bermudez continued. "I ran to see if we could help but the only thing we could see were the car lights in the front, totally smashed, almost to the ground."

Miami Mayor Carlos Gimenez said he is "actively monitoring" the "tragic situation" from abroad. He has dispatched Deputy Mayor Maurice Kemp to the scene, he said in a statement.

FIU is one of the 10 largest universities in the country, with nearly 54,000 students enrolled, according to its website.

Another press conference to share additional details has been planned for 9 a.m. EST.

This is a developing story. Check back later for more information.