After another day without finding survivors, the rescue work enters a delicate phase.

U.S.|After another day without finding survivors, the rescue work enters a delicate phase.

Following another painstaking, dangerous and ultimately fruitless day in the search for survivors, the rescue effort at the site of the Champlain Towers South collapse appeared to be entering a delicate new phase, as officials and rescuers continued to quietly acknowledge the possibility that no more victims would be found alive, though they refused to abandon all hope.

No survivors have been found since the day of the disaster in Surfside, Fla., more than a week ago, and although federal, state and local officials said they remained committed to the rescue effort, there was no sign of letup in the extraordinary challenges at the site of the condominium collapse.

Rescue workers have found it extremely difficult to tunnel through the layers of flattened concrete without putting people in danger, amid rubble that is so unstable that work was suspended for at least 12 hours on Thursday because of fears that it could collapse further. And the thunderstorms that have plagued the mission could soon worsen with the approach of Hurricane Elsa, which hammered the eastern Caribbean on Friday and could affect parts of Florida early next week, forecasters said.

Officials said on Saturday that the uncollapsed portion of the building was too unsound to withstand a tropical storm, and that they were accelerating plans to demolish it before the storm arrives. Search and rescue work was temporarily halted again at 4 p.m. Saturday because of preparations for the demolition, officials said at an evening news conference.

After meeting on Thursday with families of the missing, President Biden said: “They know that the chances are, as each day goes by, diminished slightly.”

The agencies involved in the rescue — including the Federal Emergency Management Agency, the Florida Division of Emergency Management and Miami-Dade Fire Rescue — have mostly declined to answer questions about when the search might shift to a recovery mission. Such a designation could unlock new and potentially faster ways of tunneling through the concrete to find remains, including the use of heavier machinery, and could also help families move forward in the grieving process.

On Friday, the bodies of six more victims were found, including that of the 7-year-old daughter of a Miami firefighter. Police officers, firefighters and emergency medical workers paused the search to pay their respects and flank her removal from the scene. The police did not identify the girl.

The police also confirmed the deaths of Bonnie Epstein, 56, and the married couple Maria Obias-Bonnefoy, 69, and Claudio Bonnefoy, 85.

Two of the victims found on Friday night were announced on Saturday, bringing the total to 24. As many as 121 people are still unaccounted for, a number that was revised down on Friday and again on Saturday after officials determined that some people included in earlier tallies had been located.

Publicly, rescuers and emergency medical workers refused to abandon hope. People have survived for many days after building collapses elsewhere, including after earthquakes in Haiti and Mexico. Additional urban search-and-rescue teams, activated by FEMA this week, have headed down to Surfside to assist with the effort and with hurricane preparations.

“I’m not going here right now with the hopes of finding victims — we’re going down there with the goal of finding survivors,” Ken Pagurek, the leader of Pennsylvania Task Force 1, said as he drove down to Florida on Thursday with more than 70 engineers, doctors, logistics experts and other specialists. “I still think there’s a slim chance. A slim chance is better than no chance.”