Seven men and two women died when the roof of the cave collapsed and caught them inside, the local fire brigade reports Twitter.
Only one of the 10 who were trapped in the collapsed cave survived, the newspaper reports Oglobo.
The accident happened when a group of 26 civilian firefighters participated in a training mission in a cave near Altinópolis, 300 km north of São Paulo. They were to train in cave rescue in the Dois Boca cave.
Difficult rescue work
Large resources participated in the rescue operation, but heavy rain and the danger of new collapses made the work challenging.
Several people were missing for a long time. At around 19:00 local time, the fire brigade announced that everyone had been taken out. Only one of the 10 who were missing was rescued alive.