BRASILIA (AFP) - Nine firefighters died on Sunday (Oct 31) in Brazil's Sao Paulo state after the roof of a cave in which they were training collapsed, authorities said, raising the death toll from three.

"There were nine dead and one person rescued. No more victims at the site," the Sao Paulo fire department said on Twitter.

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.

"The roof of the cave collapsed", trapping part of the group, it said.

A previous report 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 joined firefighters in a desperate effort to free those that were trapped, but the work was hampered by heavy rains.

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

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

Speaking to GloboNews, Ms Cristina Trifoni, mother of one of the instructors participating in the training, 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 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.