The Environmental Protection Agency now estimates 3 million gallons of mine waste has leaked into Colorado’s Animas River from an accidental breach of a retaining dam last week, three times the amount previously disclosed.

The contaminated sludge, which was initially released from the Gold King Mine near Silverton, Colo., by agency workers last Wednesday and Thursday, has reached Farmington, N.M., more than 100 miles downriver. The EPA said Sunday that the mine continued to discharge the waste, which contained arsenic, lead and mercury among other heavy metals, at a rate of 500 gallons per minute, according to Reuters. The EPA has been diverting the ongoing spill into two new settling ponds where the waste is being treated to lower its acidity before being discharged into a tributary, Reuters also reported.

Analysis of the spill is ongoing and while it remains unclear what health risks humans or animals face from the contaminated water, EPA toxicologist Deborah McKean said the sludge moved so quickly after the spill that it would not have “caused significant health effects” to animals that consumed the water, according to the Associated Press.

The contaminated water plume is traveling through the lands of the Navajo Nation Reservation, which stretches over 27,000 square miles in the Four Corners region of Colorado, New Mexico, Utah and Arizona. Navajo President Russell Begaye said the spill is impacting the livelihoods of his people, and has instructed the nation’s attorney general to begin preparations to file suit against the EPA. The Navajo Nation Commission on Emergency Management has also declared a state of emergency in response to the spill, the Farmington, N.M., Daily Times reported.

The EPA has not said how long cleanup efforts will take, the Associated Press reported. The EPA is looking into getting the area designated as a SuperFund cleanup site, according to the Daily Times.