Yellow coloured toxic water spilled from the Gold King Mine when an EPA cleanup team accidently triggered a large release of mine wastewater into Cement Creek.
The spill began on Wednesday when EPA workers breached the wall of Gold King Mine mine tunnel in Silverton in southwestern Colorado while trying to examine previously existing wastewater seepage.
The orange-coloured slurry water then spilled into the Cement Creek and consequently into the Animas River downstream.
Colorado Governor John Hickenlooper has also allocated $500,000 from the state’s Disaster Emergency Fund to pay for the response and technical assessments.
Hickenlooper said: "Our priority remains to ensure public safety and minimize environmental impacts.
"By declaring a disaster emergency, we are able to better support impacted businesses and communities with state resources.
"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."
New Mexico Governor Susana Martinez has also released additional funds of $750,000 following $500,000 in state emergency funds.
The funds will be used to test water wells, study the potential long-term effects of the spill, support the efforts of the multi-agency response team.
Martinez said: "I had the chance to see the spill with my own eyes. It is absolutely devastating, and I am heartbroken by this environmental catastrophe.
"As I’ve said before, I am very concerned by EPA’s lack of communication and inability to provide accurate information. One day, the spill is 1 million gallons. The next, it’s 3 million."