Rescuers on Tuesday combed through the debris of a deadly condo tower collapse in Florida as Tropical Storm Elsa threatened to complicate the delicate search mission with strong winds and heavy rain.

The death toll from the June 24 disaster in Surfside, a town north of Miami Beach, rose to 36 as search teams found four more bodies in the rubble, Miami-Dade County Mayor Daniella Levine Cava said.

Twenty-six victims have been identified.

Levine Cava said 109 people were still listed as missing and the authorities have been able to confirm that 70 of that number were in the 12-storey building when it came tumbling down.

She said Tropical Storm Elsa was making the already “challenging and adverse conditions” faced by the search teams even more difficult.

“We’re closely monitoring the weather,” the mayor said.

The National Hurricane Center said Elsa, which has maximum sustained winds of 70 miles (110 kilometers) per hour, is expected to become a hurricane before making landfall on the north Florida Gulf coast on Wednesday morning.

The authorities warned residents to prepare for storm surge and possible power outages but Surfside and the Miami area on the east coast of the state appear to have avoided the brunt of the storm.

Surfside Mayor Charles Burkett said the weather was impacting the search of the debris from the building known as Champlain Towers South.

“The wind is hampering the large cranes moving very heavy debris,” he said. “That’s a challenge they’re trying to work around right now.”

Miami-Dade County fire chief Alan Cominsky said the demolition Sunday night of the still standing portion of the building had allowed search teams to expand their operations.

Cominsky said 200 firefighters were “actively searching on the pile” with assistance from teams around the country and the world.

Cominsky said 124 tons of debris had been removed so far.

‘Deep concerns’

Burkett, the Surfside mayor, said engineers were conducting a “full structural review” of other tall buildings in the city including Champlain Towers North, a sister condo tower to the one that collapsed.

He said the authorities have “deep concerns about that building” and some residents have moved out.

“In most respects it’s the same building, built at the same time by the same owner and probably with the same materials,” Burkett said.

Levine Cava said “numerous investigations” were underway looking into the reasons for the collapse.

“The whole world wants to know what happened here,” she said. “I look forward to learning the truth, as do we all.”

“It’s very early to name any sources but of course everything is under review,” she said.

Levine Cava expressed her concern for the families that are awaiting for news about their loved ones.

“We know that the waiting, and the waiting, and the waiting is unbearable,” Levine Cava said.

No survivors have been found since the day of the collapse.

A 2018 report released by city officials revealed fears of “major structural damage” in the complex, from the concrete slab under the pool deck to columns and beams in the parking garage.

In a letter to residents in April, Jean Wodnicki, chair of the condo association, described “accelerating” damage to the 40-year-old building since then, and repairs had been set to begin soon.