EXETER, N.H. (WHDH) -- A former Exeter Hospital lab technician 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, 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. He worked in the cardiac catheterization lab from April 2011 until May.

“With Kwiatkowski’s arrest today, this serial infector has been contained and the menace he posed to public health and safety has been removed," Kacavas said. "He knew he had hepatitis C as of at least June 2010. He continued to divert drugs and permit tainted syringes to be used on patients under his care."

Investigators said Kwiatkowski injected himself with powerful painkillers meant for patients and then refilled the syringe with saline and put the tainted needles back on the shelf.

“The evidence is that he was probably alone but we’re not excluding anyone at this time because we haven’t put the fine points on our investigation,” said Kacavas.

While investigators work to determine if anyone at the hospital was involved with the potentially deadly scheme, the health department has notified over 1,000 people to be tested, and are still looking for more.

“We are still looking for 36 people that we have been unable to clearly reach and get information from them -- get in touch with them,” said Dr. Jose Montero, N.H. Department of Public Health.

Officials said Kwiatkowski’s strain of hepatitis C matches the strain of the alleged victims’.  They also say they are working with the CDC in six other states where he worked as a traveling lab tech in many other hospitals.

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

Attorney Mark Abramson is representing 14 of the infected patients. He said not only did Kwiatkowski deny patients of the pain medication, he has put the lives of people with heart conditions in greater jeopardy.

"I think he was a drug addict and this was like a kid in a candy store. He had access to all these medications," said Abramson. "Other prior institutions were aware of the fact that he had a problem. Why the Exeter Hospital never found that out, we have no idea."

Investigators said many people who have worked with Kwiatkowski have said he had to be sent home on several occasions because he was in no conditions to work with patients.

Officials said they are investigating whether someone helped Kwiatkowski obtain the drugs because a code is needed to access them.