Another body was recovered on Monday from the rubble of a collapsed Florida condominium tower, the county mayor said, bringing the death toll to 11.

Miami-Dade County Mayor Daniella Levine Cava said 150 people remained missing as of Monday afternoon as searchers continued to comb through the ruins of the building for possible survivors.

Police have so far identified eight of the victims, including a couple married for nearly 60 years and a mother whose teenage son is one of the few known survivors.

It has now been four days since a survivor was pulled alive from the ruins of the Champlain South Towers in Surfside, Florida, which abruptly collapsed on Thursday while most residents slept.

"We have people waiting and waiting and waiting. That is excruciating," Miami-Dade County Mayor Daniella Levine Cava told an afternoon news briefing, referring to friends and family members of the missing or dead.

"They are coping with the news that they might not have loved ones come out alive and still hoping that they will," the mayor said. "Their loved ones may come out as body parts."

Rescue teams were using cranes, dogs and infrared scanners to identify signs of life in the ruins, although hope was diminishing as time wore on.

Some relatives of the missing have provided DNA samples to the officials. Family members were permitted to visit the site on Sunday.

The cause of the collapse at the Champlain Towers South in Surfside, near Miami, remained under investigation.