Police have officially released the names of four people killed following the Miami bridge collapse after recovering two vehicles from the wreckage Saturday.

Authorities continue to look for bodies as word emerged that an engineer's voicemail reporting cracking in the structure wasn't discovered until Friday, one day after the collapse.

The Miami-Dade Police Department said Navarro Brown, who was among several people injured in Thursday's collapse, died in hospital. 

'Why they had to build this monstrosity in the first place to get children across the street?'  - Joe Smitha, uncle of Alex Duran

Fire and construction crews also extracted two vehicles containing bodies on Saturday from underneath the debris. The victims have been identified as:

  • Rolando Fraga Hernandez, who was in a gold jeep.
  • Oswald Gonzalez, 58, and Alberta Arias, 54, who were in a white truck.

Although other media have been reporting the names of apparent victims, police released only these four Saturday. Hernandez's and Brown's ages weren't immediately available. 

One of those named in the media, but not confirmed by police, as a victim is Alexa Duran, an 18-year-old FIU student.

On Saturday, her uncle raged against what he called the "complete incompetence" and "colossal failure" that allowed people to drive beneath the unfinished concrete span.

"Why they had to build this monstrosity in the first place to get children across the street?" said Joe Smitha. 

Authorities continued to remove debris Saturday in attempt to extract at least four cars still trapped since the span fell.

Police used cameras to locate five bodies in the rubble of the pedestrian bridge under construction at Florida International University. Authorities were carefully trying to get to remaining victims. At least six people were killed when the structure fell onto a busy highway.

"Right now we're just chipping away," said Miami-Dade police director Juan Perez.

Authorities continue to investigate the collapse and whether the cracking that was reported contributed to the bridge failure.

An engineer left the voicemail two days before the bridge collapsed, saying some cracking had been found at one end of the concrete span, but the voicemail wasn't picked up a day after the collapse, Florida Department of Transportation (DOT) officials said Friday.

The voicemail left on a landline wasn't heard by a state DOT employee until Friday because the employee was out of the office on an assignment, the agency said in an email.

Pedestrian bridge collapses onto a busy Miami highway1:15

In a transcript released Friday night, Denney Pate, with FIGG Bridge Group, says the cracking would need repairs "but from a safety perspective, we don't see that there's any issue there, so we're not concerned about it from that perspective."

On Saturday, FIU released a statement saying representatives from the university and DOT met with a FIGG engineer for two hours Thursday morning to discuss the cracking and determined there wasn't a safety issue. The bridge fell soon afterward.

"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," FIU said.

Too soon to say if cracking linked to collapse

At a news conference Friday night, officials from the National Transportation Safety Board said they have just begun their investigation, and cannot yet say whether any cracking contributed to the collapse. They also said workers were trying to strengthen a diagonal member on the bridge when it collapsed.

Robert Accetta, the investigator-in-charge for the NTSB, said crews were applying post-tensioning force, but investigators weren't sure if that's what caused the bridge to fall.

In a news release late Friday, FIGG Bridge Engineers said it "continues to work diligently" to determine the cause of the collapse, and is examining the steps its team has taken. It added, "The evaluation was based on the best available information at that time and indicated that there were no safety issues."

It also asked for time to accurately determine what led to the accident.

Florida university bridge collapse

Authorities were removing bodies from the wreckage of the collapsed bridge in Miami, but several cars were still trapped underneath the debris. (Joe Skipper/Reuters)

An FIU student who narrowly escaped from the car that got smashed in the collapse while his friend, Duran, was driving has been giving accounts to media about what led up to the tragedy.

'I looked up, and in an instant, the bridge was collapsing on us completely.' - Richie Humble, FIU student who survived bridge collapse

Richie Humble said he heard a long creaking noise coming from the structure that spanned the busy Miami-area highway. It sounded different from anything he had ever heard before.

"I looked up, and in an instant, the bridge was collapsing on us completely. It was too quick to do anything about it," Humble said Friday in a phone interview with The Associated Press.

Once Humble realized he was alive, he also realized that he could not get to Duran. He called to her. but got no response. A group of men outside the car started yelling at him to try crawling through the rear window.

He couldn't squeeze through because the window was crushed. The men outside grabbed a wooden plank and pried open the rear door to pull him free, he said.

"I was trying to get people to realize my friend was still in there," he said.

He suffered cuts to his leg from glass and a slight fracture to a vertebra, but he was able to walk away from the scene.

Did bridge cables undergo 'stress test'?

While families waited for word on their loved ones, investigators sought to understand why the 862-tonne bridge gave way during construction. The cables supporting the span were being tightened following a "stress test" when it collapsed, authorities said.

Florida bridge collapse

The death toll from the collapse rose to six from four on Friday morning. Several other people were sent to hospital. (Joe Skipper/Reuters)

The Florida DOT said in its Friday release that it had not been notified of any stress test.

Scheduled to open in 2019, the bridge would have provided safe passage over a canal and six lanes of traffic and created a showpiece architectural feature connecting the campus of FIU with the community of Sweetwater, where many students live.

The $14.2-million project was supposed to take advantage of a faster, cheaper and safer method of bridge-building promoted by the university.

​When finished, the bridge would have been supported from above, with a tall, off-centre tower and cables attached to the walkway. That tower had not yet been installed, and it was unclear what builders were using as temporary supports.

With files from CBC