A multi-level apartment block in Florida partially collapsed in the early hours of Thursday, prompting a major emergency services response.

It was unclear what caused the building to collapse and how many people were affected.

What we know so far 

Miami Dade Police said one person had died while many others were feared trapped in the rubble.

"We are working together with Miami Dade Fire and other agencies as they continue their search and rescue mission," the tweet read.

Local authorities said nearly 100 people were still unaccounted for at midday, but they did not know exactly how many were in the tower at the time of the overnight collapse.

Meanwhile the assistant fire chief of operations for Miami-Dade Fire Rescue, Raide Jadallah, said 35 people were rescued from the building and that search and rescue efforts are ongoing.

Miami Beach Police Department said its officers were "assisting the Town of Surfside at a partial building collapse." Surfside is a small waterfront town to the north of Miami Beach.

"Multiple police and fire agencies from across Miami-Dade [County] are assisting," the force added.

It is still not known how many people were in the building.

Mayor: More deaths expected

Surfside Mayor Charles Burkett said the building manager told him the tower was quite full and the death toll was likely to rise.

"The building is literally pancaked… That is heartbreaking because it doesn't mean to me that we are going to be as successful as we wanted to be in finding people alive," Burkett said.

Burkett said 10 people were treated at the scene while two others were brought to the hospital. He added that 15 families walked out of the building on their own.

Online videos showed a large portion of the 12-story building reduced to rubble, with some of the apartments' interiors exposed.

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

jsi, on/sms (AFP, Reuters)