The two affected rivers supply water to tens of thousands of people in northern Mexico.
The toxic soup first spilled into the Bacanuchi River, before entering the Sonora River and threatening water supplies for downstream communities and the state capital of Hermosillo. The pollution was first noticed by local residents who were surprised to see the Sonora River transformed into an odd, orange color. Residents also feared contamination of their groundwater.
The Attorney General for Environmental Protection said in a statement that it filed the complaint against the Buena Vista del Cobre mining company, which runs the Grupo Mexico-owned mine in Sonora state.
The office said it has also ordered an inspection of all Buena Vista del Cobre’s properties to verify the company is complying with environmental laws.
Authorities have said the Mexico chemical spill near the U.S. border was caused by defects in newly constructed leaching ponds, which hold the overflow of acids used to separate metal from crushed rock.