Several people were killed in the collapse. At least eight more were transported to nearby hospitals.
"It was like an explosion, it was like a bomb it was right behind us, it could have been us under that bridge," said witness Giovanni Hernandez.
The bridge was adjacent to Florida International University, and would have connected the campus to the nearby town of Sweetwater.
"I was sitting at the light, I was the first car, if the light would have changed I was three seconds away from being under the bridge," said Susie Bermudez.
The 950-ton section of the bridge was installed Saturday after being constructed nearby. It spanned 174 feet across a busy seven-lane road.
The bridge was assembled on the side of the road before it was moved into place. According the university, the accelerated bridge construction was supposed to reduce risks to workers and minimize traffic disruption.