Florida Highway Patrol officials said there were multiple fatalities. A final number has not been released, but at an afternoon news conference, officials said four bodies have been recovered so far.
Nine victims were transported to hospitals and eight vehicles were trapped underneath the bridge after the collapse.
Fire officials said rescue crews were expected to be at the scene for the rest of the night or longer.
The school issued a statement on the tragic event, saying they are "shocked and saddened" and are still involved in rescue efforts.
UPDATE:Company that constructed pedestrian bridge at @FIU issues statement: "Our family’s thoughts and prayers go out to everyone affected by this terrible tragedy." https://t.co/fACPvnRcrL pic.twitter.com/jCVdt1LP4g— ABC7 Eyewitness News (@ABC7) March 15, 2018
The FIU-Sweetwater pedestrian bridge was installed on Saturday, according to an FIU press release.
The 174-foot, 950-ton bridge was installed within hours using "accelerated bridge construction" methods, which the university said "reduces potential risks to workers, commuters, and pedestrians and minimizes traffic interruptions."
The $14.2 million bridge crossed over a busy seven-lane road that divided the university's campus from the city of Sweetwater.
Gov. Rick Scott tweeted that he was on his way to the scene.
"I will be in constant communication with law enforcement throughout the day," the governor said.
MCM, the Miami-based construction management firm who won the bridge contract, took its website down on Thursday. But an archived version of the website featured a news release touting the project.
Florida International University is the second-largest university in the state, with 55,000 students. Most of its students live off-campus and the bridge was supposed to be a safe way to cross a busy street and a plaza-like public space with seating where people could gather.
In August 2017, a university student was killed crossing the road that the bridge was supposed to span.
Florida International University is also home to the National Hurricane Center.
ABC News and the Associated Press contributed to this report.