CONCORD, N.H. (AP) — The probe into a hepatitis C outbreak at Exeter Hospital’s cardiac catheterization lab reached the courts Thursday, with the attorney general’s office announcing a criminal investigation and a civil lawsuit being filed on behalf of one of the infected patients.

Twenty people, including a hospital worker, have been diagnosed with the same strain of the liver-destroying virus since state public health officials began investigating last month.

On Wednesday, public health director Dr. Jose Montero said evidence so far points to drug diversion as the likely cause, which generally involves someone using a syringe to inject medication meant for someone else and then re-using the syringe on patients.