Hundreds of fire and rescue workers are scouring tonnes of rubble after a 12-storey oceanfront apartment building partially collapsed in southern Florida.
At least one person is dead and 99 remain unaccounted for, officials say.
Sally Heyman, a Miami-Dade County Commissioner, initially said officials had been unable to make contact with 51 people who “supposedly” live in the building.
That figure was later revised up to 99 missing and 102 accounted for.
“The hope is still there but it’s waning,” Ms Heyman said.
The building is home to a mix of people, including families and part-time “snow birds” who spent the northern winter in Florida.
A fire official said 35 people were rescued from the building in Surfside, a seaside enclave of 5700 residents on an island across Biscayne Bay from Miami.
They included two who were pulled from the rubble as response teams used trained dogs and drones in a search for survivors.
After speaking with local officials, Florida Governor Ron DeSantis said it was possible that more victims could be found in the rubble.
He said he planned to go to the scene.
“We’ll hope for the best in terms of additional recoveries but we are bracing for some bad news, just given the destruction that we’re seeing,” Mr DeSantis said from an event near Tampa.
Built in 1981, the Champlain Towers South had more than 130 units, about 80 of which were occupied.
It was unclear how many people were inside at 1.30am Thursday (local time) when an entire side of the building pulled away and fell to the ground below.
“It’s hard to imagine how this could have happened,” Surfside Mayor Charles Burkett said.
“Buildings just don’t fall down.”
Construction work was being done on the roof, he said, but it was unclear whether the project involved any heavy gear.
Footage from WPLG Local 10, a Miami TV station, showed a rescue team pulling a boy from piles of debris and firefighters using ladder trucks to rescue residents trapped on balconies.
Assistant Fire Chief of Miami-Dade Fire Rescue Raide Jadallah said that rescuers were moving in “heavy equipment” and working to support the remaining structure of the building.
“We are still continuing the search and rescue operations,” he said.
Mr Burkett said part of the building with balconies facing the beach “pancaked”, with one floor appearing to have fallen one top of another as they cascaded down.
“The back of the building, probably a third or more, is totally pancaked,” he said.
Miami-Dade Police have taken control of the investigation.
More than 80 fire and rescue units responded, the Miami-Dade County Fire Rescue Department wrote in a Twitter message early on Thursday.
Eyewitness video obtained by Reuters showed neighbours gathering across the street from the rubble.
“This whole building here, it’s completely gone,” a person can be heard saying.
Photos and video from the scene show that the collapse affected half the tower. Piles of rubble and debris surrounded the area just outside the building.
Police blocked nearby roads, and scores of fire and rescue vehicles, ambulances and police cars swarmed the area.
NOW: Partial-building collapse in Surfside Florida near Miami Beach. Miami/Dade Fire and Rescue Team searching for bodies. This is horrific.pic.twitter.com/pwLy5fepR0
— Katie Daviscourt🇺🇸 (@KatieDaviscourt) June 24, 2021
-with AAP, agencies