A state of emergency was declared on Monday after more than three million gallons of toxic waste water was accidentally released from a defunct Colorado gold mine into local streams.
The water has turned parts of the Animas River an unsightly mustard yellow colour, and is threatening to reach as far as Lake Powell in Utah, which provides large parts of America's southwest with drinking water.
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The spill is believed to have been inadvertently triggered by a team of Environmental Protection Agency (EPA) workers.
CNN reports that the spill occurred when one of its teams was using heavy equipment to enter the Gold King Mine. Instead of entering the mine and beginning the process of pumping and treating the contaminated water inside as planned, the team accidentally caused it to flow into the nearby Animas River.
According to the Daily Telegraph, Colorado Governor John Hickenlooper said $500,000 would be released from a state fund to treat the spill, which contains high concentrations of arsenic, mercury and lead.
USA Today reports that officials have advised residents with wells in the floodplains to have their water tested before drinking it or washing in it.
EPA officials are also consulting with representatives from the Navajo Nation, whose reservation borders affected areas in Farmington and the San Juan River.
Navajo Nation Council speaker LoRenzo Bates said that residents were concerned about drinking water safety, river access, water for livestock and crops, and the possibility of compensation for failed crops.
He added that with irrigation canals shut off, many farmers are concerned about what will happen next.
Mr Hickenlooper added: "We will work closely with the EPA to continue to measure water quality as it returns to normal, but also to work together to assess other mines throughout the state to make sure this doesn't happen again."
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