Four firefighters were admitted to hospital on Friday after battling the overnight blaze at Badim Hospital and about 90 patients were transferred to other hospitals, the fire department said.

Most victims died of asphyxiation as smoke filled the wards, and some died when life support equipment stopped working in the fire, said Gabriela Graca, director of the state Institute of Forensic Medicine.

When firefighters arrived, they evacuated people but it was more difficult to move patients who were hooked up to medical equipment, according to reports.

Camila Donato, a police spokeswoman, said police were cleared by firefighters to enter the hospital and had begun investigating the case.

As the fire burned, medical workers in surgical masks rolled equipment in the road as smoke billowed from the building. Television images showed staff tending to patients sitting in wheelchairs with IV poles beside them in the street, some on sheets and mattresses.

Intensive care patients were among those rescued.

In the chaos, distraught relatives tried to track down patients, unsure of whether they had perished in the fire or had been transferred to another medical facility.

Authorities released a list of names of 10 of the dead, some in their 80s and 90s.

Marcelo Crivella, the mayor of Rio de Janeiro, said a total of 11 people died. He declared an official mourning period of three days.

Australian Associated Press