DENVER (AP) - Federal authorities say a former surgery technician may have exposed thousands of Colorado patients to Hepatitis C when she swapped her own dirty syringes for ones filled with a powerful narcotic.

Kristen Diane Parker faces Federal criminal charges for allegedly making the swaps while working at Audobon Ambulatory Surgery Center in Colorado Springs and Rose Medical Center in Denver.

Authorities say Parker admitted to changing out syringes with a saline solution with ones filled with the painkiller Fentanyl.

Parker injected herself with the drug, a seven page complaint filed Thursday in U.S. District Court in Denver says.

An affidavit says at least nine surgery patients at Rose have tested positive for the Hepatitis C, which is incurable. About 6,000 patients are being advised they may have been exposed and need to be tested.