CNN —  

A Colorado hospital says a former employee may have exposed patients who had surgery there to hepatitis B, hepatitis C and HIV.

Swedish Medical Center in Englewood, Colorado, said Wednesday about 2,900 patients should get tested for the viruses.

Hospital officials did not detail how the patients could have been put at risk. The medical center said it began contacting patients who had surgery at the hospital between August 17, 2015, and January 22, 2016, as part of an investigation into a former employee who may have stolen narcotic pain medication intended for patients.

The hospital has no evidence of any patient exposure to the viruses but wants to be cautious, Swedish Medical Center spokeswoman Nicole Williams said.

“We deeply regret that one of our former employees may have put patients at risk, and are sorry for any uncertainty or anxiety this may cause,” Richard A. Hammett, the hospital’s president and CEO, said in a written statement. “Please know our first concern is the health, care, safety and privacy of our patients and we are working diligently to look after the well-being of the patients who may have been affected by the wrongful actions of this individual.”

Authorities haven’t identified the former employee who is the focus of the investigation. Hospital officials said they were working with state public health officials and police and that criminal charges are possible.

In 2009, a surgical technician at another Colorado hospital infected 19 patients with hepatitis C after she injected herself with syringes that held their pain medication, then replaced the pain medication in their syringes with saline. Kristen Diane Parker pleaded guilty to a number of federal charges and was sentenced to 30 years in prison.