The first two vehicles, flattened beyond recognition and with three bodies inside, were extricated from the wreckage of a collapsed pedestrian bridge near Miami yesterday morning, as workers continued to dig through the rubble.

The three bodies were among the six fatalities believed to have occurred in the collapse Thursday afternoon, but authorities said that number could rise as vehicles are removed. Of the eight vehicles caught beneath the 950-ton bridge, six were trapped entirely, with four being "very difficult to extract," said Maurice Kemp, deputy mayor of of Miami-Dade County.

"We're open-minded to the fact that we may find more victims than we initially projected," Kemp said at a news briefing near the site yesterday.

Flatbed trucks carried the vehicles, draped in black tarps, to the medical examiner's office, where the remains of the three victims would be identified, according to Miami-Dade Police.

Miami-Dade Fire Rescue Department personel and other rescue units work at the scene of the bridge collapse. Photo / AP
Miami-Dade Fire Rescue Department personel and other rescue units work at the scene of the bridge collapse. Photo / AP

The bridge collapsed while under construction over a busy road between the campus of Florida International University and a neighboring city.

Late Friday, Florida officials revealed that a lead engineer for the private contractor on the project had left a voicemail message for a Florida Department of Transportation official two days before the bridge fell, warning of "some cracking."

The engineer, who works for FIGG Bridge Engineers, reported that he did not consider it a safety issue. The official didn't hear the message until Friday, after the collapse, because he had been out of the office on assignment, the state transportation agency said.

FIGG Bridge Engineers, which designed the span, said in a statement Friday night it is "carefully examining the steps that our team has taken in the interest of our overarching concern for public safety."

The company added - in an apparent reference to its engineer's conclusion that safety was not an issue - that "the evaluation was based on the best available information at that time."

On Thursday, shortly before the bridge collapsed, a consultant to the transportation department met with members of the team responsible for the project. The consultant was not notified of a safety problem, the transportation department said.

"The responsibility to identify and address life-safety issues and properly communicate them is the sole responsibility of the FIU design build team," the transportation department said. "At no point during any of the communications above did FIGG or any member of the FIU design build team ever communicate a life-safety issue."

The university later added a more detailed recollection of the Thursday meeting. It was convened by FIGG and Munilla Construction Management (MCM), which built the bridge, "to discuss a crack that appeared on the structure," the university said.

"The FIGG engineer of record delivered a technical presentation regarding the crack and concluded that there were no safety concerns and the crack did not compromise the structural integrity of the bridge," the university said in a statement, adding that representatives of the school and the transportation department attended the session, which lasted two hours.

At the Saturday morning briefing, FIU President Mark Rosenberg didn't expand on the fact that FIU had known about the report of cracking.

"We are cooperating fully with the authorities in this investigation," Rosenberg said.

Asked whether he believed reporting the cracking to the state through a voicemail message represented "due diligence," Rosenberg declined to comment, citing the ongoing investigation.

Juan Perez, director of the Miami-Dade Police Department, referred questions about the investigation to the National Transportation Safety Board.

Perez said chaplains were with victims' families. Workers recognised moments of silence as vehicles were brought out, he said, "so these victims can have some dignity."

Authorities "obviously have an idea of who is in these vehicles," Perez said, but they would be taken to the medical examiner's office for "100 per cent identification."

"It's going to be a long process," Perez said of the removal of trapped vehicles. "We've been saying that from the begining because of the amount of weight and the size of the structure that is laying on top of these vehicles."