At least 10 people were killed Friday in a fire that broke out in a defunct hotel being used as a makeshift homeless shelter in the city of Porto Alegre in southern Brazil, officials said.

Emergency workers confirmed 10 victims at the site, which was operating without proper authorization, said the fire department for Rio Grande do Sul state, whose capital is Porto Alegre.

"Forensic experts are at the scene to identify the victims and investigate the cause of the fire," it said in a statement.

State Governor Eduardo Leite said the fire, which broke out around 2:00 am (0500 GMT), had left him "deeply upset."

"The fire department dispatched five trucks and dozens of firefighters to fight the flames," he wrote on X, formerly Twitter.

"We will continue working on the aftermath of this tragedy and the investigation of the causes. My condolences to the victims' families."

Images in Brazilian media showed the three-storey building engulfed in flames as firefighters battled to extinguish them.

Mayor Sebastiao Melo wrote on X that multiple injured victims were rescued and taken to the hospital, but did not say how many. Local media reports put the number of injured at 11, some in serious condition.