SURFSIDE, June 29 (Reuters) - Another body was recovered on Tuesday from the ruins of a Florida condominium tower, the mayor said, raising the death toll in the collapse to at least 12 with 149 people still listed as missing.

The latest casualty of the disaster, which could ultimately rank as the worst accidental building collapse in U.S. history, was not immediately identified by Miami-Dade County Mayor Daniella Levine Cava during an afternoon news conference.

Investigators have not yet determined what caused a major section of the 40-year-old building to collapse abruptly. Initial attention has focused on structural deficiencies described in a 2018 engineer's report.

In April 2021, the condominium association's president warned residents that concrete damage had "gotten significantly worse," and urged them to pay some $15 million in assessments needed to make repairs, media reported.

Florida emergency management director Kevin Guthrie said local authorities on Tuesday had asked the federal government to send additional urban search and rescue teams to the scene in the town of Surfside.

Authorities say they still have hope that survivors might yet be found in the pile of concrete and twisted metal left when nearly half of the 12-story, 136-unit tower caved in.

“The rescue effort continues unabated except for that brief lightning storm we had today,” Surfside Mayor Charles Burkett said.

No one has been pulled alive from the ruins of the oceanfront Champlain Towers South since a few hours after one side of the high-rise collapsed early on Thursday morning as most residents slept.

Fire officials have spoken of detecting faint sounds from inside the rubble pile and finding voids deep in the debris large enough to possibly sustain life.

But Miami-Dade Fire Rescue Chief Alan Cominsky said search-and-rescue personnel faced an enormous task while working 12-hour shifts in the heat.

“That building collapsed almost in a footprint of where that building stood – we’re talking about 12 stories, with subterranean garages all within that same footprint,” Cominsky said. “I'm sure to emphasize the magnitude of what we encountered, what we're seeing,” he told reporters.

Rescue workers have moved 3 million pounds of concrete piece by piece from the debris since the collapse, Cominsky said. The teams include experts sent by Israel and Mexico to assist in the search.

President Joe Biden and his wife, Jill Biden, will visit Surfside on Thursday, the White House said.