A former New Hampshire hospital employee was charged Thursday with causing a hepatitis C outbreak involving patients who were treated at the hospital’s cardiac catheterization lab.

U.S. Attorney John Kacavas said David Kwiatkowski, 33, a former lab technician at Exeter Hospital, has been charged with fraudulently obtaining drugs and tampering with a consumer product. He was arrested at a hospital in Massachusetts, where he’s receiving medical treatment.

Kacavas said Kwiatkowski, originally from Michigan, worked as a traveling medical technician in at least six other states. He had been at Exeter since April 2011.

“This serial infector has been contained and the menace he posed to public health and safety has been removed,” Kacavas said.

Investigators believe he stole syringes containing an anesthetic and injected himself with them. He then put another liquid, such as saline, into the syringes, which were later injected into the patients.

Kacavas said the investigation revealed that Kwiatkowski was involved in a similar incident at a hospital in another state. He was not specific.

Altogether, 31 people, including Kwiatkowski, have tested positive for the same strain of the disease since the investigation began in late May.

Hepatitis C is a blood-borne viral infection that can cause liver disease and chronic health issues.