Mexican authorities have imposed restrictions on water supplies in some cities and towns in the northern part of the country, including the Sonora state capital of Hermosillo, following a spill of contaminated wastewater from the nearby copper mine.
Contaminated wastewater from Buenavista del Cobre, a copper mine owned by Grupo Mexico, reportedly spilled into the Bacanuchi River in north-west Mexico, killing fish and livestock.
The National Water Commission (Conagua) was quoted by InterAksyon.com as saying: "The mine spilled approximately 40,000m³ (1.4 million ft³) of leached copper into the Bacanuchi River, a tributary of the Sonora River."
According to authorities, the toxic substance included sulphuric acid, which turned the river water into orange colour.
Following the leak, federal officials restricted the water supply to seven municipalities in the country's north-west region. Other affected towns include Arizpe, Banamichi, San Felipe de Jesus, Aconchi, Baviacora and Ures.
The National Water Commission is monitoring chemicals in the Bacanuchi and Sonora rivers.
Meanwhile, the Federal Attorney for Environmental Protection (PROFEPA) of Mexico has ordered the mining firm to contain the spill by neutralising the sulphuric acid with lime, pumping out the contaminated water and building dams to prevent future spills.
Sonora State accounts for 27% of all mining in the country and produces minerals such as gold, copper, graphite and other mined products.