PORTLAND — Two New Hampshire residents pleaded guilty Wednesday to charges stemming from a string of armed bank robberies in Maine and New Hampshire.

Crystal Dufault, 33, and Joseph Richards, 46, both of Manchester, New Hampshire, pleaded guilty to armed bank robbery and conspiracy to commit armed bank robbery in a case investigated by several area law enforcement agencies, including some from York County, according to a press release from U.S. Attorney Thomas E. Delahanty II.

Both Dufault and Richards were charged with robbing Franklin Savings Bank in Franklin, New Hampshire, on Aug. 14, and University Credit Union in Portland on Sept. 4. Richards was also charged with robbing Norway Savings Bank in Freeport on Aug. 3 and TD Bank in Lewiston on Sept. 12.

According to court documents, a pellet gun was brandished during each of the robberies, and the pair netted a total of almost $38,000.

The defendants face up to 25 years in prison and a $250,000 fine on each charge. They will be sentenced after completion of a pre-sentence investigation report prepared by the U.S. Probation Office.

The joint investigation was conducted by police departments in Saco, Old Orchard Beach, Freeport, Portland and Lewiston in Maine; the Franklin and Manchester, New Hampshire, police departments; the Maine State Police; and the Southern Maine Gang Task Force.

The latter was comprised of agents and officers from the Federal Bureau of Investigation; the Bureau of Alcohol, Tobacco, Firearms and Explosives; the U.S. Drug Enforcement Administration; U.S. Immigration and Customs Enforcement’s Homeland Security Investigations; and the Portland, South Portland, Lewiston and Biddeford police departments.