A newly installed pedestrian bridge over a major road in Miami collapsed, killing four people and trapping multiple cars below.
The walkway, which connected Florida International University to a student housing area, went up less than a week ago but was not yet operational.
"We have located up to four victims. Four deceased," Miami-Dade Fire Chief Dave Downey told a news conference.
Crews worked into the night at the scene of the disaster. Maurice Kemp, the area's deputy mayor, said the search for survivors had not been abandoned.
"Miami-Dade county and our partner agencies... have been working feverishly in the search and rescue mode to ascertain how many victims there are and rescue as many as we can," Kemp told journalists.
Miami-Dade Fire Rescue Division Chief Paul Estopinan said at least eight cars were trapped when the 950-ton (tonne) concrete bridge suddenly gave way.
Police detective Juan Carlos Llera said, "it sounded like an explosion. A huge bang."
Isabella Carrasco, who said she arrived on the scene just after the collapse, told CNN that some cars were completely crushed, and there was "just a lot of debris everywhere."
Another shaken driver, Lynnell Collins, told CNN he was about to make a right turn when "the whole thing really just came down."
"After the whole thing broke, I was freaking out. I got out of my car and me and a few other people were sprinting over there. We started helping people whose cars were at least half crushed and whoever was easily saved."
He said he saw two trucks that were "completely crushed."
"At this time we are still involved in rescue efforts and gathering information."
"In our 40-year history, nothing like this has ever happened before."