About a million gallons of water from a closed gold mine was released into the upper portions of Cement Creek in San Juan County, CO when officials from the U.S. Environmental Protection Agency (EPA) and the Colorado Division of Reclamation, Mining and Safety accidently triggered the release while working to secure the entrance to the Gold King Mine.

Cement Creek is a tributary of the Animas River.

The EPA said that a cleanup team was working with heavy equipment to secure the mine entrance at the time of the release, NBC News reported.

"The project was intended to pump and treat the water and reduce metals pollution flowing out of the mine," EPA spokesman Rich Mylott said in a statement.

The creek runs into the Animas River, which then flows into the San Juan River in New Mexico and joins the Colorado River in Utah.

Officials emphasized that there was no threat to drinking water from the spill. But downstream water agencies were warned to avoid Animas water until the plume passes, said David Ostrander, director of EPA’s emergency response program in Denver.

Officials were not sure how long it would take the plume to dissipate, Ostrander said. The acidic sludge is made of heavy metal and soil, which could irritate the skin, he said.

The EPA was testing the plume to see which metals were released. Previous contamination from the mine sent iron, aluminum, cadmium, zinc and copper into the water, said Peter Butler, co-coordinator of the Animas River Stakeholders Group.

The EPA said in a statement that the polluted water “was held behind unconsolidated debris near an abandoned mine portal.”