'Horrific catastrophe': At least one dead, dozens unaccounted for in Miami

More than 50 people are thought to be missing after a 12-storey building partially collapsed in Miami, leaving at least one person dead and 10 others injured.

Miami-Dade Commissioner Sally Heyman said 51 people who were assumed to have been living in the partially collapsed part of the building have not been accounted for.

She told CNN those people have "not either called out or had people call in to reach them" but it was unclear if they had all been in the building when it collapsed about 2am (4pm AEST) on Thursday, because of "vacations or anything else".

"We're still waiting and unfortunately the hope is still there, but it is weaning," she said.

Charles Burkett, mayor of the Miami council of Surfside, said the cause had not yet been determined but a collapse of this nature was "less likely than a lightning strike".

"This is a horrific catastrophe. In the United States, buildings just don't fall down," Cr Burkett said.

The mayor told reporters 10 people were treated at the scene and the building had been cleared. But he said half of the building's 130 units had collapsed and it was unclear how many people were missing.

Cr Burkett went on to say the building was undergoing roof work but he couldn't say whether that was a contributing factor to the collapse.

"We are afraid the building may be in danger of additional collapse," he told CNN affiliate WSVN.

"The problem is the building has literally pancaked. It has gone down and I mean, there's just feet in between storeys where there were 10 feet (about 3m).

"That is heartbreaking because it doesn't mean to me that we are going to be successful, as successful as we want to be to find people alive."

Surfside Town Manager Andy Hyatt said the search and rescue process could take a week and Florida Governor Ron DeSantis warned the city was "bracing for some bad news just given the destruction that we're seeing".

'How could anybody survive this?'

Footage from the ground showed fire crews pulling one survivor, a teen boy, from the rubble.

Nicholas Balboa was walking his dog when he heard the boy and eventually found him "sticking his hand up through the debris".

"I was thinking to myself, 'how could anybody survive this?' As I was thinking that, I heard a voice yelling," he said.

Balboa said he and another person climbed up the rubble to help, and then found police and firefighters to help.

Fears for missing loved ones

The collapse sent a cloud of debris through the neighbourhood, coating cars up to two blocks away with a light layer of dust.

Authorities have not revealed how many people live in the building, but some witnesses in the exclusion zone say they fear friends or loved ones are still inside.

Kimberly Morales said she lived in the building across the street from the collapse and was awakened by building alarms going off and pounding on her door.

"I woke everyone up in the room because when I looked out the window, I saw everyone outside," she told CNN.

"I told everyone to hurry up and leave the building."

When part of his residential building collapsed, Barry Cohen knew he needed to get out of his apartment. But when he looked down the hallway, he said, "there was nothing there".

"It was just a pile of dust and rubble and paint falling from the ceilings," he told CNN.

After not being able to find a way out of the building, he said he went to his balcony, and by that time, the fire trucks and police had arrived.

"When we were waiting for the firetruck to approach the building, the building was still shaking," he said.

"It just seemed like it was very unsteady. And I just, you know, knowing how what it looked like outside my door, I thought that any minute, we could be that same pile of rubble."

Authorities still on the scene

Police blocked nearby roads, and scores of fire and rescue vehicles, ambulances and police cars swarmed the area.

"We're on the scene so it's still very active," Surfside Police Department Sergeant Marian Cruz said.

"What I can tell you is the building is 12 floors. The entire back side of the building has collapsed."

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.

The department has yet to say what may have caused the collapse near 88th Street and Collins Avenue.

"I have never seen so many ambulances and police in my life all at once," a man who lives nearby told CNN.

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"It looked like something from 9/11, literally.

"The entire building collapsed from the 14th floor.

"So there's a third of the entire building, that you cannot see from the street, but it's completely gone.

"It almost looks like 9/11 or if a bomb hit or something.

"It just completely wiped it out. There's a pile of rubble."

Survivors evacuated

Survivors and those from surrounding buildings have been evacuated to a nearby community centre as crews work to find anyone else alive.

According to the Miami Herald, the 12-storey condo tower, part of Champlain Towers, is an oceanside condo built in 1981 with more than 100 units.

The area is a mix of new and old apartments, houses, condominiums and hotels, with restaurants and stores serving an international combination of residents and tourists.

The community provides a stark contrast from bustle and glitz of South Beach with a slower paced neighbourhood feel.

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