(Bloomberg) -- Authorities in Brazil are cracking down on illegal copper mining in the Amazon as high prices of the wiring metal attract black-market operators who normally focus on gold.

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Earlier this month, 50 agents dismantled illicit mines in Canaa dos Carajas — near Vale SA’s biggest copper mine, Sossego — after two similar actions last year. There are signs the metal has been shipped to China, task-force leader Ezequias Martins said via his press office. The case may lead to convictions for environmental crimes and criminal association, he said.

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Unlicensed miners, known in Brazil as garimpeiros, have diversified into copper in recent years as techniques improve and prices surge on growing battery-metal demand in the shift away from fossil fuels. At the same time, major mining companies are looking to add copper assets. Vale wants to raise money to grow its base metals business.

While illegal production accounts for a tiny portion of total copper supply, it can have an outsized impact on the environment and indigenous communities. President Luiz Inacio Lula da Silva’s government has vowed to crack down on Brazil’s illegal gold rush, with non-government organization MapBiomas estimating that irregular operations now occupy a larger area than industrial mines in the country.

The clandestine copper mines demobilized this month are the so-called gallery type, in which explosives are used to blast out ore containing copper and gold. Some galleries can extract 30 tons a day. Copper trades at about $9,000 a ton in London versus less than $5,000 three years ago.