An engineer reportedly found cracks in a new pedestrian bridge at Florida International University in the Miami two days before it collapsed on Thursday, killing at least six people.

An engineer with the firm that designed the bridge left a voicemail with the Florida Department of Transportation reporting “some cracking that’s been observed on the north end of the span,” though he did not believe it to be an immediate safety concern. An employee at the Florida Department of Transportation did not receive the voicemail until after the bridge’s collapse, reports the Miami Herald.

The National Transportation Safety Board, which is investigating the disaster, has not determined whether the cracks had anything to do with the bridge’s collapse.

Installed Saturday, the bridge was constructed to give pedestrian access over the Tamiami Trail, a busy stretch of Florida highway that claimed an undergraduate student’s life last August. While the university does offer shuttles between campus and the neighboring town, the bridge was being built to connect the campus with the town of Sweetwater, where thousands of students live.

The bridge was installed using what was hailed as an innovative construction method — “accelerated bridge construction,” or “instant bridge” — which was meant to reduce risk to workers and pedestrians and prevent traffic in the area. Over the past several months, the bridge was assembled on the side of the trail while support towers were put in place on either side of the highway; then it was picked up and positioned over the road in a matter of hours. The plan was expected to be finished in early 2019 and include a plaza and wifi.

The project, funded by the US Department of Transportation, cost $14.2 million and was part of a larger “prosperity” initiative led by the university. Infrastructure has been identified as one of the Trump administration’s priorities, despite a lack of urgency to actually push the issue in Congress.

The White House released a “What you need to know about Infrastructure Funding” briefing, touting the president’s infrastructure proposal, just minutes after the news in Florida. It’s not clear whether the release was intentionally timed with the accident.

Here’s what we know and don’t know about the bridge collapse.

What we know

The bridge, which was installed on Southwest Eighth Street near 109th Avenue, collapsed Thursday at 1:45 pm ET.

At least six people have been killed, Miami-Dade Fire Rescue officials confirmed Friday morning. An 18-year-old FIU student was among the deceased, reports the Miami Herald.

Nine victims were taken to area hospitals, Miami-Dade Fire Chief Dave Downey said at a Thursday evening press conference.

Cars and people were trapped underneath the bridge. Five to eight vehicles were crushed, highway patrol said.

THE FIU BRIDGE COLLAPSED OH MY GOD pic.twitter.com/JO7jfx5AoN — Gabriela Collazo (@GabrielaRose12) March 15, 2018

Miami-Dade Fire Rescue officials ended search and rescue operations and began recovery efforts Friday, determining no survivors remain trapped, according to the Washington Post.

Juan Perez, the Miami-Dade Police chief, said Thursday his department will take over the homicide investigation. “This is going to be a long, long process,” Perez said.

First responders and detectives are taking pictures of the scene from up top the #fiubridge. @MiamiHerald pic.twitter.com/RLeqarJXVP — Monique O. Madan (@MoniqueOMadan) March 16, 2018

The bridge weighs 950 tons and was installed Saturday as part of a pedestrian safety initiative, to reduce foot traffic on the busy Tamiami Trail highway underneath. The bridge was a partnership between MCM Construction and FIGG Bridge Design, which also developed the Sunshine Skyway Bridge over Tampa Bay.

The project cost $14.2 million and was funded through a $19.4 million grant from the US Department of Transportation.

An engineer with the firm that designed the bridge reported cracks in the structure just two days before it collapsed. He reported his finding to a Florida Department of Transportation employee, leaving a voicemail, which the FDOT employee did not hear until Friday. It remains unclear whether this had anything to do with the span’s failure.

In the voicemail, the engineer says he observed “cracking ... on the north end of the span, the pylon end of that span we moved this weekend,” according to a transcript released by the Florida Department of Transportation, and published by the Miami Herald. In the voicemail, he also explained that “obviously some repairs or whatever will have to be done” but said that “from a safety perspective we don’t see that there’s any issue there so we’re not concerned about it from that perspective.”

The Florida Department of Transportation has released preliminary findings, which said that “due to the unique characteristics of the design of the bridge” a secondary, independent review was required. However, the firm contracted to do this review, Louis Berger, was not pre-qualified by the state transportation department, reports the Miami Herald.

FDOT releases 'preliminary findings' and says that FIU design team hired a firm to do a 'design check' that was not pre-qualified with the state, as required by the contract. pic.twitter.com/8stvDSBF2a — Mary Ellen Klas (@MaryEllenKlas) March 16, 2018

According to Sen. Marco Rubio, the cables suspending the pedestrian bridge had loosened and were being tightened when the bridge collapsed. Investigations continue to find the cause of the collapse.

The National Transportation Safety Board (NTSB) is sending a team to investigate.

President Donald Trump responded to the bridge collapse on Twitter. “Praying this evening for all who are affected,” he wrote.

Continuing to monitor the heartbreaking bridge collapse at FIU - so tragic. Many brave First Responders rushed in to save lives. Thank you for your courage. Praying this evening for all who are affected. — Donald J. Trump (@realDonaldTrump) March 15, 2018

What we don’t know

The final number, or the identities of all the victims

The extent of injuries

The extent of the damage