An innovative pedestrian bridge being built at Florida International University was put to a "stress test" before it collapsed over traffic, killing six people and sending 10 to a hospital, authorities said.
As state and federal investigators worked to determine how and why the five-day-old span failed on Thursday, one factor may have been the stress test that Miami-Dade Mayor Carlos Gimenez said crews were conducting on the span. Two workers were on the 950-ton bridge when it pancaked on top of vehicles waiting at a stoplight.
First responders had been racing to find survivors in the rubble of the 175-foot span using high-tech listening devices, trained sniffing dogs and search cameras before turning the scene over to police.
"This has turned from a rescue to a recovery operation," Miami-Dade Police Det. Alvaro Zabaleta said.
The $14.2 million pedestrian bridge was supposed to open in 2019 as a safe way to cross a busy six-lane road between the university campus and the community of Sweetwater, where many students live.
Florida Gov. Rick Scott and U.S. Sen. Marco Rubio joined other authorities at the scene. Rubio said the public and the families of the dead and injured deserve to know "what went wrong."
Scott added an investigation will get to the bottom of "why this happened and what happened," and that if anyone did anything wrong, "we will hold them accountable."
The White House said President Donald Trump is aware of the bridge collapse and is monitoring the situation. Trump tweeted his support to first responders and families affected by the accident.
National Transportation Safety Board chairman Robert Sumwalt III said a team of specialists would begin its investigation Friday morning.
Rubio, who is an adjunct professor at the school, noted the pedestrian bridge was intended to be an innovative and "one-of-a-kind engineering design."
Renderings showed a tall, off-center tower with supporting cables attached to the walkway. When the bridge collapsed, the main tower had not yet been installed, and it was unclear what builders were using as temporary supports.
An accelerated construction method was supposed to reduce risks to workers and pedestrians and minimize traffic disruption, the university said. The school has long been interested in this kind of bridge design; in 2010, it opened an Accelerated Bridge Construction Center to "provide the transportation industry with the tools needed to effectively and economically utilize the principles of ABC to enhance mobility and safety, and produce safe, environmentally friendly, long-lasting bridges."