An engineer left a voicemail two days before a catastrophic bridge failure in Miami to say some cracking had been found at one end of the concrete span, but the voicemail was not picked up until after the collapse, Florida Department of Transportation (DoT) officials have said.
The voicemail left on a landline was not 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.
In a transcript released on 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".
At a news conference on Friday night, officials from the National Transportation Safety Board (NTSB) said they have just begun their investigation, and cannot yet say whether that cracking contributed to the collapse. They also said workers were trying to strengthen a diagonal member on the pedestrian bridge at Florida International University (FIU) when it collapsed.
Robert Accetta, the investigator-in-charge for the NTSB, said crews were applying post-tensioning force, but investigators are not sure if that is what caused the bridge to fall.
In a news release late on 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.
The bridge collapsed on Thursday, killing at least six people. Authorities are slowly removing the debris and looking for more victims.
A college student who narrowly escaped from a car that got smashed by a collapsing bridge said he watched helplessly as the structure tumbled down on top of the vehicle and killed the friend who was sitting next to him in the driver's seat.
Richie Humble, who studies at FIU, was riding in a car under the pedestrian bridge when he heard a long creaking noise coming from the structure that spanned a busy Miami-area road. 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," Mr Humble said in a phone interview with The Associated Press.
Rescuers are looking for the young woman who was at the wheel, Alexa Duran, whose family said she was dead. Once he realised he was alive, Mr Humble also realised that he could not get to Ms 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 made his way into the back seat but could not 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 realise 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.
While families waited for word on their loved ones, investigators sought to understand why the 950-ton bridge gave way during construction. The cables supporting the span were being tightened following a "stress test" when it collapsed, authorities said.
"This is a tragedy that we don't want to re-occur anywhere in the United States," said Juan Perez, director of the Miami-Dade police. "We just want to find out what caused this collapse to occur and people to die."
Detectives declared the rubble a homicide scene, and the NTSB arrived to investigate.
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.
Authorities have not confirmed the victims' names. The fatalities included a student at FIU. One person died at a hospital, and Mr Perez said five bodies were located with the help of cameras but had not yet been retrieved.