US President Joe Biden will visit the site of a deadly apartment block collapse in southern Florida later this week, the White House announced Tuesday, as rescuers scoured the wreckage in the increasingly desperate search for survivors.

"On Thursday, July 1, the president and the first lady will travel to Surfside, Florida," the administration said in a statement, adding that details for the trip would be provided later.

The death toll from last Thursday's collapse of the oceanfront apartment building stood at 11 on Tuesday, with 150 still unaccounted for, leaving desperate families fearing the worst.

Rescue work continued day and night at the remains of the 12-story Champlain Towers South
Rescue work continued day and night at the remains of the 12-story Champlain Towers South AFP / Giorgio VIERA

Biden said Sunday his administration would coordinate with local officials and was "ready to provide any support or assistance that is needed."

"This is an unimaginably difficult time for the families enduring this tragedy," he said in a statement.

Experts are looking at possible pre-existing critical flaws in the structure of the apartment tower, which pancaked into a pile of smoking rubble as residents were sleeping in the early hours of Thursday.

Rescue teams from Florida and abroad have worked around the clock to scour the debris for signs of life, but the outlook has grown increasingly grim, with no one emerging alive from the rubble in the aftermath.

Florida building collapse
Florida building collapse AFP / Tatiana MAGARINOS

"The search continues, and it will not stop until there is a resolution," Florida Governor Ron DeSantis told reporters Monday.

Friends and neighbors of the building's occupants held a vigil on a nearby beach on Monday evening, clutching white roses and sobbing as a facilitator burned incense and played a gong.

Glow sticks and dirt laid on the sand spelled out the word "HOPE," while down the coast at the ruins of the building, the sound of rescuers' power tools carried on through the night.

An October 2018 report released by city officials late Friday revealed fears of "major structural damage" in the Champlain Towers South complex, from the concrete slab under the pool deck to the columns and beams in the parking garage.

Repairs had been set to begin soon in the 40-year-old building -- but did not come soon enough.

Jean Wodnicki, the chairman of the condo association described "accelerating" damage to the building since then, in a letter to residents in April.

Israeli and Mexican engineers and search-and-rescue specialists have joined an army of American workers at the site, backed by two huge cranes and sniffer dogs.