New Hampshire’s top federal prosecutor said Thursday that additional people could be charged as the investigation continues into how a 33-year-old medical technician was able to steal drugs that led to the spread of hepatitis C to at least 39 patients nationwide, mostly at Exeter Hospital.

John Kacavas, the US attorney for New Hampshire, declined to specify who else might be implicated beyond David M. Kwiatkowski, the medical technician who was indicted by a grand jury Wednesday. But investigators combing through records have identified colleagues who worked with Kwiatkowski on cases, as well as staffers at personnel agencies and hospitals who played a role in his employment.