More than 160 Nigerians have died because of lead poisoning from illegal gold mining in the nation’s north.

Nigeria’s chief epidemiologist, Henry Akpan, told CNN 163 Nigerians, including 111 children, have died in the Zamfara state after falling sick while trying to extract gold from rock deposits in the region.

Decontamination efforts have begun and illegal mining has since stopped, according to reports.