Federal prosecutors have said a hospital surgery technician accused of stealing painkiller syringes is HIV positive and have urged patients who may have been infected by him to be tested.

Rocky Allen has pleaded not guilty to charges that he took a syringe of painkillers and replaced it with one containing another substance at Swedish Medical Center in suburban Denver.

Prosecutors previously referred to him as having an undisclosed “blood-borne pathogen” during a February court hearing.

The fear is that Allen may have replaced needles intended for patients with syringes he has previously used, meaning patients could have been infected.

Swedish Medical Center where Rocky Allen worked as a surgery technician

Allen worked at the Swedish Medical Center over a five-month period

Public health officials have said the risk of exposure to blood-borne pathogens is low, and there have been no reported cases of patients becoming infected because of Allen.

Timothy O’Hara, a lawyer for Allen, said evidence showed he may have switched syringes, but there was no reason to believe he was re-using them.

Authorities say Allen was seen taking a syringe filled with painkillers from an operating room at the hospital on 22 January.

He was fired, and three weeks later federal prosecutors charged him with tampering with a consumer product and obtaining a controlled substance by deceit.

Prosecutors allege he has a history of moving from hospital to hospital and lying about his past to steal drugs.

Court records show he has been fired from at least three hospitals in Arizona, California and Washington. Patients who were treated there have also been advised to be tested.

Military records show Allen had drug problems when he served in the Navy. He was court-martialled in 2011 for stealing pain medication.

Colorado health officials have said Swedish Medical Center attempted to notify around 3,000 patients who underwent surgery in the hospital’s main operating room while Allen was employed there – between August 2015 and January this year.

Dr Larry Wolk, chief medical officer and executive director of the Colorado Department of Public Health and Environment, said test results were not obtained for around 1,000 of those patients.

No evidence of transmission was found in those with completed testing.

Mr O’Hara said Allen suffered from post-traumatic stress disorder after serving as a Navy medical worker in Afghanistan, where he started using drugs.

Nicole Williams, a spokeswoman for the hospital, said problems found in an April investigation report were not directly related to the Allen case and a subsequent review found “zero deficiencies”.