A special task force in Brazil is conducting raids deep in the Amazon, in a new crackdown against what it calls "blood gold" mining.
Mining in territories that are supposed to be protected by law is destroying the lives of indigenous people and wreaking havoc on the environment.
The UK is the third biggest buyer of Brazilian gold, and public prosecutors have alleged that 30% of Brazil’s exports may be illegally mined.
The BBC was given exclusive access to film a rare special forces operation. The identities of some of the operatives have been protected.