SURFSIDE, United States: Four people are now known to have died in the collapse of an oceanfront apartment block near Miami Beach, officials said Friday, while the number of unaccounted for has risen to 159 -- fueling fears of a much higher death toll.

An unknown number of residents are feared to have been asleep in the 12-story building in the town of Surfside, when one of its wings was reduced early Thursday morning to a gigantic pile of debris.

"We do have 120 people now accounted for, which is very, very good news. But our unaccounted for number has gone up to 159," Miami-Dade County mayor Daniella Levine Cava told a news conference.

"In addition, we can tragically report the death count is now four," she said, adding that the numbers were "very fluid."

Rescue teams with sniffer dogs worked through a second night despite heavy rain -- clinging to the diminishing chance of finding additional survivors.

Their efforts were illuminated by lights shining on the debris, with the recovered bodies put into yellow bags and transported away as homicide detectives worked to confirm their identities.

More rain is expected Friday.

"We will continue search and rescue because we still have hope that we will find people alive," said Levine Cava -- who described the dedication of the dozens of rescuers on site as "incredibly moving."

"They are totally, totally motivated to find people. They have to be pulled off the shift. That is how motivated they are to continue their efforts."

President Joe Biden declared an emergency early Friday in response to the disaster, ordering federal assistance for the local relief effort.

At a Surfside community center on Thursday night, relatives of the missing wept as they waited for news. Tenants of the ruined building who were lucky enough to have been away when disaster struck pondered sudden homelessness.

Erick de Moura, 40, happened to spend Wednesday night at his girlfriend's house.

"I just came back and the scene is shocking," he said. "There is a lot of pain. I'm blessed that I am alive."

   **- 'Bracing for bad news' -**

Around 55 apartments were affected by the collapse, with emergency services arrived at the scene at around 1:30 am on Thursday, evacuating 35 people from the building.

"One side of the building just fell completely. It doesn't exist anymore," said Nicolas Fernandez, 29, an Argentinian resident of Miami who had yet to hear from friends who were staying overnight in his family's unit in the building.

"I don't know about them. I don't know if they are alive," he told AFP.

The building was occupied by a mix of full-time and seasonal residents and renters, and officials have stressed it is unclear how many people were actually inside at the time.

Some residents were able to walk down the stairs to safety while others had to be rescued from their balconies.

"It's a really, really tragic situation so we'll hope for the best in terms of additional recoveries, but we are bracing for some bad news just given the destruction that we're seeing," Governor Rob DeSantis warned Thursday.

   **- 'Building exploded' -**

Officials said the reasons for the collapse were still unclear.

Fernandez, the Argentinian resident of Miami, said that when his mother called him in the early hours to say the building had collapsed, he thought it was a joke -- and hung up.

"She calls me again and tells me: 'Nico, you know I would never joke about this. I need you to go over there.' We came running."

One witness, 25-year-old Julian Targowski, described the sound of the collapse.

"Like, a ton of bass on a subwoofer, basically," he said. "Then my friend texted me that a building had exploded."

Local media said records showed the block was built in 1981 and had more than 130 units inside.

Miami-Dade County officials have confirmed that the building had been undergoing construction work on its roof, but have stressed the reasons for the collapse remain unclear.