This view of the Gold King Mine on Aug. 9, 2015, shows orange wastewater  in a settling pond.

(Grace Hood/CPR News)

Colorado officials are disputing a key claim by federal agencies about a massive spill of toxic wastewater from an inactive mine.

A report by the federal Bureau of Reclamation said two state mining experts signed off on an Environmental Protection Agency cleanup project that led to the Aug. 5 spill at the Gold King Mine in southwest Colorado.

But Mike King, head of the state Department of Natural Resources, says the state experts with the Division of Reclamation Mining and Safety neither approved nor disapproved the operation.

"DRMS did not have any authority to manage, assess, or approve any work at the Gold King Mine," King wrote in a letter. 

Later in the letter, King concludes: "...[O]perations at Gold King were entirely under EPA management using EPA contractors on an EPA response action..."

The letter, which The Associated Press obtained through an open records request, is a blow to the EPA's contention that outside experts supported the plan.

The EPA said Thursday it's reviewing King's letter. The Bureau of Reclamation said the author of its report wasn't available to comment.