This photo from an EPA report shows water from the collapsed Gold King Mine overtaking trucks and heavy equipment before it flows into Cement Creek and the Animas River on Aug. 5, 2015.

(Courtesy EPA)

The U.S. Attorney’s Office in Colorado has declined to prosecute an Environmental Protection Agency worker involved with the Gold King Mine spill. The office looked into whether the unnamed EPA worker had violated the Clean Water Act and made false statements in 2015 after the spill.

An EPA-led cleanup team inadvertently caused the blowout while working at the Gold King Mine above Silverton in August of 2015. The spill turned the Animas River a bright orange and also tainted waterways in New Mexico and Utah.

Since the agency has decided to not prosecute the worker, the EPA’s watchdog arm, the Office of Inspector General, will instead prepare a report for the EPA’s top leadership to review. The probe was driven by Republican members of Congress. On Wednesday, several Republicans sent a letter to the Department Of Justice requesting a briefing to explain how officials arrived at their decision. They say the EPA’s Office of Inspector General found evidence of wrongdoing and they want to understand why the DOJ decided not to prosecute.