SAO PAULO (AP) — An Indigenous group in Brazil said Wednesday its members detained 12 people for allegedly mining illegally in the Amazon and handed them over to police.

The non-profit Urihi Associação Yanomami said in a statement that the incident took place Tuesday in the northern state of Roraima, which borders Venezuela. The organization said its move was aimed at avoiding the risk of water contamination by mercury in mining.

Brazil’s Indigenous Peoples Ministry confirmed that a dozen alleged miners, including 10 men and two women, were in police custody.

The Yanomami group filmed some of its members carrying bows and shotguns as they took the alleged miners to police. The detainees did not make comments in the video. The Associated Press could not find a spokesperson for them.

The Yanomami community is the Amazon’s largest Indigenous tribe living in relative isolation, and many of its members are contaminated with mercury coming from widespread illegal gold mining, according to Brazil’s top public health institute.