Water authority chief Oscar Cristi said in an exclusive interview that regulators had stopped issuing new permits to extract water from the southernmost sector of the Salar’s watershed, known as C2.

Which is a key water supply for BHP’s (BHP.AX) Escondida copper mine, the world’s largest, and Antofagasta (ANTO.L)’s Zaldivar mine.

Cristi said the government had granted BHP and Antofagasta permits to pump six times more water from an aquifer at Atacama than it could sustain, prompting the ban. BHP has since proposed to cut water extraction from wells in C2 by more than half.

But Cristi said regulators still believed that rate to be “insufficient.”