(MIAMI) — At least one person was killed and several others were injured early Thursday after a 12-story residential building partially collapsed in southern Florida’s Miami-Dade County, authorities said.

The Miami-Dade Fire Rescue received a call at around 1:30 a.m. local time about a partial collapse of the Champlain Towers South condominium in the small, beachside town of Surfside, about 6 miles north of Miami Beach. A massive search and rescue operation was launched before dawn, as crews carefully combed through the wreckage and remaining structure for survivors. So far, crews have rescued 35 occupants who were trapped inside the building and two others who were located beneath the rubble, according to Miami-Dade Fire Rescue Assistant Chief Ray Jadallah.

“We are shoring up the structure on the inside as we continue to tunnel in to locate additional survivors,” Jadallah said during a press conference in Surfside on Thursday morning.

Footage from the scene showed firefighters pulling a boy from the rubble alive and rescuing other people from still-standing balconies.

Jadallah told reporters that at least 45 people, including those who were rescued, were medically assessed and treated on site. Two of them were subsequently transported to local hospitals, and one has since died.

Aventura Hospital and Medical Center, about 8 miles northwest of Surfside, has received three patients from the scene so far. Two have critical injuries while the third is in fair condition, a hospital spokesperson told ABC News.

The oceanfront condominium has 136 units, and approximately 55 of them collapsed on the northeast corridor, according to Jadallah. The Miami-Dade Fire Rescue has sent more than 80 units to the scene and is leading the search and rescue efforts, which Jadallah said “are still ongoing.” It was unclear how many residents were unaccounted for.

Witnesses told Miami ABC affiliate WPLG that more people are still trapped inside the building.

Multiple police and fire departments from across Miami-Dade County have been deployed to the scene to assist.

Surfside Mayor Charles Burkett told reporters that the condominium was built in the 1980s and was believed to be substantially full at the time of the partial collapse. The building was undergoing roof work, he said.

Some 15 families escaped the building on their own and were put up in a local hotel, according to Burkett. Search dogs did an initial pass around the wreckage when it was still dark and the site was considered dangerous, but there were no signs of survivors at that time, the mayor said.

Miami-Dade County Mayor Daniella Levine Cava called the situation “unimaginable” and thanked the “brave” rescuers.

“We need to allow them to do their work because every minute in this search can make a huge difference,” Levine Cava said during the press conference in Surfside on Thursday morning.

Florida Gov. Ron DeSantis told reporters that he has spoken to local officials regarding the incident in Surfside and plans to travel to the scene soon.

“It’s a really, really tragic situation, so we’ll hope for the best in terms of additional recoveries,” DeSantis said during a press conference in Tampa on Thursday morning. “But we are bracing for some bad news, just given the destruction we are seeing.”

One witness told ABC News that his wife cares for an elderly woman who lives in the condominium and frantically called him around 1:15 a.m. local time, after the units next door came crashing down. He said his wife and the elderly woman were both rescued.

People in neighboring buildings have been evacuated to a local recreational center, another witness told ABC News.

The cause of the partial collapse was unknown. The Miami-Dade Police Department is leading the investigation into the incident.

“Our goal is to provide a thorough investigation and closure for our families,” Freddy Ramirez, director of the Miami-Dade Police Department, said during the press conference in Surfside on Thursday morning.

Authorities have opened a family assistance center at the Surfside recreational center for individuals unable to locate loved ones who live in the Champlain Towers South. Anyone with family members from the condominium who are either safe or still missing is urged to call 305-614-1819 to account for them.

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