Richard D. Morrison Jr., 21, of Tunkhannock, and Richard Thomas Medders, 22, of Trussville, Ala., were arrested Saturday along with Janna Rebecca Lynn Smith, 27, of Richlands, N.C., police said. They remained in custody Monday in lieu of $100,000 bail each.
They were charged with conspiracy to risk a catastrophe, a felony, plus misdemeanor charges of making bomb threats and terroristic threats.
Prosecutor George Skumanick said they were turned in by a sister of Morrison.
"Morrison's sister and a friend heard them talk about this and observed them on the Internet," Skumanick told the News & Observer of Raleigh, N.C. The newspaper did not identify the sister.
Morrison and Medders allegedly left Camp Lejeune about two weeks ago, state police said.
It was not clear if they were authorized to be off base. Marine Corps officials did not return calls seeking comment Monday.
Tunkhannock is about 135 miles northwest of Philadelphia.