Rescue crews near Miami are combing through tons of rubble for anyone who may have survived the pre-dawn collapse of part of an oceanfront residential tower, with officials reporting at least one person found dead and nearly 100 more missing.
Emergency responders and officials were still looking for people who might be in the rubble, as well as trying to identify residents who were not home at 1.30am on Thursday when an entire side of the 12-storey building gave way and fell to the ground.
Sally Heyman, a Miami-Dade County Commissioner, said officials have been unable to make contact with 51 individuals who "supposedly" live in the building, home to a mix of people including families and part-time "snow bird" residents who spend the winter months in Florida.
Miami-Dade Police Director Freddy Ramirez later told reporters that 99 people were unaccounted for and that 53 others whose whereabouts were initially unknown have since been located, though he did not make clear whether everyone in the second group was alive.
"Fire and rescue are in there with their search team, with their dogs. It's a very dangerous site right now. Very unstable," Ramirez told reporters. "They're in search-and-rescue mode, and they will be in that mode for a while. They are not quitting. They're going to work through the night. They are not stopping."
Ramirez said the numbers of known casualties and people missing were likely to fluctuate. "I don't want to set false expectations," he said. "This is a very tragic situation for those families and for the community."
A fire official said 35 people were rescued from the building in Surfside, a seaside enclave of 5700 residents on a barrier island across Biscayne Bay from the city of Miami, including two who were pulled from the rubble as response teams used trained dogs and drones in the search for survivors.
Officials said the building, built in 1981, was going through a recertification process requiring repairs and that another building was being built next door, although the cause of the collapse remained unclear.
"We have 51 people that were assumed to have been there, but you don't know between vacations or anything else, so we're still waiting," Heyman told CNN by phone earlier in the day. "The hope is still there, but it's waning."
The search effort was slowed by at least one fire that burned at the site as emergency crews doused the rubble with water, local media reported. The Champlain Towers South had more than 130 units, about 80 of which were occupied. It had been subject to various inspections recently due to the recertification process and the adjacent construction of a building called 88 Park.
The Miami-Dade Police have assumed 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.
Marco Bello and Rich McKay - AAP