Just days after workers with the Environmental Protection Agency (EPA) accidentally spilled a million gallons of toxic mine waste into a Colorado waterway, the free-flowing sludge that turned portions of the state’s Animas River orange reached New Mexico, where health and wildlife officials say they were not alerted to any impending contamination.

As the cities of Aztec and Bloomfield scrambled to cut off the river’s access to water treatment plants, they criticized the EPA for what they said was a lackluster effort in providing warnings or answers about the spill. The contaminants seeping into the river—at a rate of 548 gallons per minute—include arsenic, copper, zinc, lead, aluminum, and cadmium.

The Animas flows into the San Juan River in New Mexico, which in turn joins the Colorado River in Utah’s Lake Powell.

Workers unleashed the waste while using heavy machinery to investigate toxic materials at Colorado’s non-functioning Gold King Mine. But the accident, while “unexpected” by EPA’s admission, is a reminder that defunct mines still heavy with contaminates exist throughout the West.

The Associated Press writes:

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There are a number of factors which contribute to the abandonment of such sites. One is cost, as cleaning up toxic materials can be an expensive endeavor. But more complex is the legal liability involved. According to the Clean Water Act, anyone who “[d]ischarges a pollutant from a point source into a water of the United States” without a permit can be prosecuted for a federal crime, even if they were trying to clean up pollution. That has prevented green groups from engaging in those cleanup efforts—particularly as an ongoing push for a “Good Samaritan” exception to the law has gone ignored by the federal government, AP writes.

“There’s still a whole generation of abandoned mines that needs to be dealt with,” Steve Kandell of Trout Unlimited, one of the organizations backing the “Good Samaritan” bill, told the AP.