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

A 12-story oceanfront condominium in Surfside, a neighborhood near Miami, pancaked into rubble in the early hours of Thursday last week, with the official death toll of 11 expected to rise as hope dwindles for 150 people still unaccounted for.

The White House said the president would visit the site with First Lady Jill Biden on Thursday to ensure state and local officials have everything they need for the rescue effort.

"They want to thank the heroic first responders, search-and-rescue teams, and everyone who's been working tirelessly around the clock," said press secretary Jen Psaki.

The first couple also wants to "meet with the families who have been forced to endure this terrible tragedy, waiting in anguish and heartbreak for word of their loved ones, to offer them comfort as search and rescue efforts continue," she said.

Residents in the part of Champlain Towers South that remained intact reported being awakened around 1:30 am (0530 GMT) Thursday by what sounded like cracks of thunder that shook their rooms.

Rescuers who arrived in the moments after the tower came down helped evacuate dozens of residents, and pulled one teenage boy alive from the rubble.

But authorities have faced mounting anger in the days since the disaster from friends and family who have received no further news of loved ones feared trapped beneath the smoking wreckage.

Underscoring the slow pace of progress in the "painstaking, grueling" search for survivors, Miami-Dade County Mayor Daniella Levine Cava said Tuesday that the death toll had not risen overnight from 11.

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

"There are currently 210 people working on the site. The urban search and rescue team has been augmented by teams from all over the state and all over the world," Levine Cava said.

"They are working throughout inclement weather. They are working as hard as they ever have."

The outlook has nevertheless grown increasingly grim, with no one emerging alive from the rubble in the aftermath.

- 'Unimaginably difficult' -
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 apartment block, the sound of rescuers' power tools carried on through the night.

Experts are looking at possible pre-existing critical flaws in the structure of the apartment tower.

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

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

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

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.