Sinaloa, Mexico - A retention dam collapsed at a gold and silver mine in Mexico's northern state of Sinaloa, causing nearly 11,000 tons of toxic material to pollute nearby rivers.

Roughly 10,800 tons of toxic material from the "Two Gentlemen" mine leaked into the Chupaderos stream, which flows into the Baluarte River in the town of Concordia, local authorities reported on Friday.

State and federal authorities have taken emergency measures to prevent wastes pollutants from contaminating ground water and affecting inhabitants of the region.

The Federal Attorney for Environmental Protection (PROFEPA,) said the discharge of the toxic materials occurred Thursday morning due to a "collapse" at the mine’s dam, however the agency was not notified until three hours later. The composition of the toxic materials has yet to be disclosed.

In a statement, the agency explained that the chemical material has thus far covered a distance of over half a mile down the slope of the outside of the dam. The mine is located just north of Culiacan, the capital city of Sinaloa.

PROFEPA also noted that it will open an administrative proceeding so as to plan for eventual remediation of the site which will be authorized by the Ministry of the Environment and Natural Resources.

On August 8th, ten million gallons of toxic wastewater spilled from the Buenavista copper mine in Cananea, polluting the Bacanuchi and Sonora rivers and affecting the water supply of more than 22,000 people. SEMARNAT’s director, Juan Jose Guerra Abud, called the spill the country’s "worst industrial mining disaster."

That spill caused public outrage and protest, with organizations and politicians calling for hard sanctions and costs be paid by mining giant Grupo Mexico.

Over that spill, organizations such as Greenpeace warned that remediation will not fully clean up the spill and heavy metals will remain, causing prolonged and possibly permanent environmental damage and serious health risks to neighboring populations.