MIAMI—A bridge built to save lives has instead caused at least six deaths after collapsing onto a busy roadway at Florida International University on Thursday.

The FIU-Sweetwater UniversityCity Bridge spans an eight-lane highway and collapsed onto eight vehicles, according to an eyewitness and television footage. At least six people were killed and nine were taken to the hospital, officials told reporters. The cause of the collapse is not yet known, but the National Transportation Safety Board said it is investigating.

The bridge gave way at about 2 p.m. while a row of vehicles was stopped at a red light, the Miami Herald reported. First responders rushed directly to the pile of crushed concrete and twisted steel, including medical personnel from the nearby hospital.

“I saw the bridge-collapse workers walking over top, trying to get under the rubble,” Andrew Hyder, a 22-year-old IT student at FIU, told The Daily Beast. “You could see several cars trapped underneath the bridge, police all up and down Southwest 8th. Pretty crazy stuff.”

Hyder lives on the top floor of an apartment building directly overlooking the bridge from across a small canal. He didn’t hear the collapse because he was wearing headphones. When a friend called him, he saw the dozen or so frantic texts from loved ones on his phone and went to his balcony.

Apart from the sound of emergency sirens, the typically bustling FIU campus was otherwise quiet on Thursday due to spring break.

“I can only imagine if it wasn’t spring break,” Hyder said.

The bridge’s span was lowered into place on Saturday but not scheduled to open until early 2019, according to the Herald.

The bridge was erected using “Accelerated Bridge Construction” (ABC), meaning components were constructed adjacent to the roadway in order to reduce building time. The rapid installation happened “in a single morning” after “months of preparation,” according to the Herald.

The method “reduces potential risks to workers, commuters, and pedestrians and minimizes traffic interruptions,” according to FIU News.

The 174-foot, 950-ton span and was meant to “provide students a safe route over the perilous roadway for the first time,” according to the Herald. Students and teachers had requested it be built after an FIU undergraduate, Alexis Dale, was fatally hit by a car in August while crossing the highway.

Earlier this week, FIU President Mark Rosenberg said, “FIU is about building bridges and student safety. This project accomplishes our mission beautifully.”

Rep. Mario Diaz-Balart (R-FL), who spoke at a ceremony commemorating the bridge on Saturday, told reporters on Capitol Hill that Thursday’s collapse was “beyond catastrophic.”

“There are going to be a lot of questions that have to be answered,” he said. “It’s just devastating.”

The bridge was a project of MCM Construction and FIGG Bridge Design—the firm behind the Sunshine Skyway Bridge in Tampa Bay. It was funded by a grant from the U.S. Department of Transportation to the tune of $14.2 million, according to the Herald.

“This project is an outstanding example of the ABC method,” Atorod Azizinamini, an FIU professor who is reportedly an expert in ABC, told FIU News. “Building the major element of the bridge—its main span superstructure—outside of the traveled way and away from busy Eighth Street is a milestone.”

MCM released a statement on Thursday afternoon offering “thoughts and prayers.”

“We are devastated and doing everything we can to assist,” it said. “We expect a full investigation will follow; we will cooperate in any way.”

FIGG Engineering added, “In our 40-year history, nothing like this has ever happened before. Our entire team mourns the loss of life and injuries associated with this devastating tragedy, and our prayers go out to all involved.”

—with additional reporting from Andrew Desiderio