At least one person was killed and many others were pulled from rubble after a beachfront condo building partially collapsed outside Miami on Thursday.
A wing of the 12-storey building in the community of Surfside came down with a roar around 1:30am.
By late evening, nearly 100 people were still unaccounted for, authorities said, raising fears that the death toll could climb sharply.
Officials did not know how many were in the tower when it fell.
Surfside mayor Charles Burkett said: “The building is literally pancaked.
“That is heartbreaking because it doesn’t mean, to me, that we are going to be as successful as we wanted to be in finding people alive.”
Hours after the collapse, searchers were trying to reach a trapped child whose parents were believed to be dead.
In another case, rescuers saved a mother and child, but the woman’s leg had to be amputated to remove her from the rubble, Frank Rollason, director of Miami-Dade emergency management, told the Miami Herald.
Video showed fire crews removing a boy from the wreckage, but it was not clear whether he was the same person mentioned by Mr Rollason.
Teams were trying to enter the building from a parking garage beneath the structure.
Governor Ron DeSantis, who toured the scene, said television did not capture the scale of what happened.
Rescue crews are “doing everything they can to save lives. That is ongoing, and they’re not going to rest,” he said.
Teams of 10 to 12 rescuers at a time entered the rubble with dogs and other equipment, working until they grew tired from the heavy lifting, then making way for a new team, said Florida chief financial officer Jimmy Patronis, the state’s fire marshal.
He told Miami TV station WPLG: “They’re not going to stop just because of nightfall. They just may have a different path they pursue.”
Authorities did not say what may have caused the collapse. On video footage captured from nearby, the centre of the building appeared to fall first, with a section nearest the ocean teetering and coming down seconds later as a huge dust cloud swallowed the neighbourhood.
Work was being done on the building’s roof, but Mr Burkett said he did not see how that could have been the cause.
President Joe Biden promised to provide federal aid if requested.
Hotels opened to some displaced residents, the mayor said, and deliveries of food, medicine and more were being hastily arranged.
About half of the building’s roughly 130 units were affected, the mayor told a news conference.
Rescuers pulled at least 35 people from the rubble by mid-morning, and heavy equipment was being brought in to help stabilise the structure to provide more access, Raide Jadallah of Miami-Dade Fire and Rescue said.
The tower has a mix of seasonal and year-round residents, and while the building keeps a log of guests, it does not keep track of when owners are in residence, Mr Burkett said.
Nicholas Fernandez spent hours after the collapse trying to call two friends who were staying in the building with their young daughter.
The family had come to the United States to avoid the Covid-19 outbreak in their home country of Argentina, said Mr Fernandez, of Miami.
“The hope is that, perhaps, someone hears the call. I know there are dogs inside,” he said.
“I know it may sound ridiculous what I’m saying but there’s always hope until we hear different.”
A total of 22 South Americans were missing in the collapse — nine from Argentina, six from Paraguay, four from Venezuela and three from Uruguay, according to officials in those countries.
The collapse, which appeared to affect one leg of the L-shaped tower, tore away walls and ripped open some homes in the still-standing part of the building.
TV footage showed beds, tables and chairs inside. Air conditioners hung from some parts of the building, where wires dangled.
Barry Cohen, 63, said he and his wife were asleep in the building when he first heard what he thought was a crack of thunder.
The couple went onto their balcony, then opened the door to the building’s hallway to find “a pile of rubble and dust and smoke billowing around”.
The former vice mayor of Surfside said: “I couldn’t walk out past my doorway.”
Surfside city commissioner Eliana Salzhauer told WPLG that the building’s county-mandated 40-year re-certification process was ongoing.
Ms Salzhauer said the process was believed to be proceeding without difficulty. A building inspector was on-site Wednesday.
She said: “I want to know why this happened. That’s really the only question … And can it happen again? Are any other of our buildings in town in jeopardy?”
The seaside condo development was built in 1981.
The area’s neighbourhood feel offers a stark contrast to the glitz and bustle of nearby South Beach.
The area has a mix of new and old apartments, houses, condominiums and hotels, with restaurants and stores serving an international combination of residents and tourists.