Rescuers are desperately searching for any survivors trapped in the rubble of a collapsed 12-storey residential building north of Miami.
At least one person has been killed and 99 are still missing, officials say.
As families desperately wait for news, search teams have been working around the clock and have reported hearing people banging beneath the debris.
What caused the 40-year-old building to collapse early on Thursday morning remains unclear.
At least 102 people have now been accounted for, but it is uncertain how many were in the building when it came down. Dozens of survivors have been pulled out of the rubble.
President Joe Biden has approved an emergency declaration for Florida, meaning the Federal Emergency Management Agency will help state agencies with the relief effort.
As night fell, hundreds of rescuers were using sonar cameras and specially trained dogs as they scoured the rubble for survivors. Teams were tunnelling from an underground car park below the building in an effort to reach victims.
"Fire and rescue are in there with their search team, with their dogs," Miami-Dade Police Director Freddy 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."
Search teams detected sounds of banging and other noises, but no voices coming from the tonnes of debris.
But officials say the efforts are dangerous as further rubble could collapse on top of them.
"This process is slow and methodical," said Ray Jadallah, Miami-Dade Fire Rescue assistant fire chief. "Any time we started breaching parts of the structure, we get rubble falling on us."
Constant rain and storms are further complicating an already difficult task for the search-and-rescue teams.