Rescue crews are searching for survivors after an entire side of the 12-storey building in the Miami community of Surfside gave way while residents were asleep. At least one person is dead and about 100 are missing.

Joseph Waks believes an elderly Australian couple he's known for many years was in the building at the time.

He has not heard from them since the collapse and has been waiting at the scene for updates from police.

"We're hoping for the best, we're hoping there'll be a miracle," he has told the ABC.

He said the couple was originally from Sydney but later moved to Melbourne and divided their time between Australia and Miami, where they have family.

"They have been in and out of this community for many, many years," he said.

"It's devastating. They both became grandparents yet again a few hours before the tragedy. We still cannot believe it."

Danny Rivero, a reporter from National Public Radio in South Florida, tweeted on Friday: "We've been told many Argentinians and Australians were in the building as well, and that all are unaccounted for. This is an international disaster."

The Department of Foreign Affairs and Trade said it was aware of reports Australians may have been caught up in the disaster at the Champlain Tower South Condominium.

"The Australian embassy in Washington is closely monitoring developments and making urgent enquiries to determine if any Australians were affected," it said.

Surfside is a community of 5700 residents with a large Jewish presence.

The Australian Jewish Association has been in contact with a committee member who is in Miami, staying near the collapsed building.

There are no reports so far of any Australian Jews being caught up in the disaster, a spokesman for the association told AAP.

Australian Associated Press