The attack has highlighted a growing risk for miners in the Andean nation, the world's no.
"Security is now one of the main costs," Poderosa corporate affairs manager Pablo de la Flor told Reuters after the attack.
Thousands of trucks of illegal gold were taken out, it said.
"There is a black market for minerals," said Gustavo Ramirez, who studies illegal mining for SNMPE.
Illegal miners are estimated to produce around another 30 tons.
Persons:
Cristobal Bouroncle, Rights LIMA, Pablo de la Flor, De la Flor, Saturday's, la Flor, Poderosa, Gustavo Ramirez, Marco Aquino, Alexander Villegas, Marguerita Choy
Organizations:
Rights, Reuters, National Society of Mining, Petroleum, Energy, Peru's Ministry of Energy, Mining, Ministry of Energy, Mines, Thomson
Locations:
Madre de Dios , Peru, Peru, Pataz, India, Switzerland, Canada, Bolivia