Jul. 3, 2009 (United Press International) -- Thousands of patients in Colorado may have been exposed to hepatitis C from syringes used by an infected former medical technician, officials say.

Rose Medical Center in Denver is offering free testing to more than 4,700 former patients. Another 1,000 people may have been exposed at Audubon Ambulatory Surgery Center in Colorado Springs where the technician worked after being fired from Rose in April, The Denver Post reported Thursday.

The technician was fired after having failed a drug test. Identified by The (Colorado Springs) Gazette newspaper as Kristen Diane Parker, 26, of Colorado Springs, based on Justice Department documents. The documents said she was in federal custody after allegedly swapping her used, dirty syringes, refilled with saline solution, for ones filled the painkiller fentanyl.

Hospital officials knew she had hepatitis C when she was hired in October and fired in April before state health officials alerted the hospital to the infections, the newspaper said. Hospital officials stressed that the fired employee was not confirmed to be the infection's source.

State health authorities have determined nine former Rose patients tested positive for the disease and are still investigating, Rose officials said.