The U.S. Attorney General's office will not prosecute an Environmental Protection Agency employee for his involvement in a Colorado mine wastewater spill caused by the agency that polluted rivers in three western states last year.

The EPA's Office of Inspector General said Wednesday that it found evidence the unnamed employee may have violated the Clean Water Act and given false statements. But spokesman Jeff Ladga said the Justice Department will not pursue the case. Instead, the case will be sent to the agency's leaders.

"The EPA is required to report to the Office of Inspector General any administrative action taken as a result of the Report On Investigation," according to a statement issued by EPA Office of Inspector General spokesman Jeff Ladga.

The investigation has been ongoing for more than a year following the Aug. 5, 2015, blowout of the Gold King Mine in southwestern Colorado. Federal officials had opened a criminal probe after members of Congress demanded accountability of EPA employees for triggering the spill of 3 million gallons of toxic metals that sullied the waterways in Colorado, Utah and New Mexico.