Brazilian authorities said Sunday that nine firefighters had died in a cave after the roof collapsed while they were training inside.

The accident occurred as a group of 26 firefighters were on a training exercise in a cave near the city of Altinopolis, the Sao Paulo fire department said on Twitter.

"There were 9 dead and one person rescued. There are no more victims at the site," it said.

Earlier, officials had said there were three dead and six missing. The identities of the victims were not disclosed.

A previous report from the Altinopolis mayor's office said 15 firefighters were still buried, and that three of the victims who were rescued suffered fractures and hypothermia.

Five people in total were taken to a local hospital and discharged, according to the mayor's office.

Police and emergency health teams had joined firefighters earlier Sunday in a desperate effort to free those still trapped, but the work was hampered by heavy rains.

Access to the remote site was difficult, and threats of new collapses complicated the rescue attempts.

Sao Paulo Governor Joao Doria had said on Twitter he would provide "all the support and resources necessary for the rescue of the victims."

Speaking to GloboNews, Cristina Trifoni, mother of one of the instructors participating in the training event, explained that the group had planned to spend the night inside the cave.

"What happened is that the entrance to the place they were in collapsed. I'm desperate," she said, standing next to relatives of other firefighters who anxiously awaited word on the rescue effort.

Altinopolis is known for its caves, a major regional tourist attraction.