DEERFIELD, Massachusetts (Reuters) - A Maine man pleaded guilty on Friday to federal charges stemming from threats to rape, torture and kill hosts of a popular National Public Radio Program.

John Crosby, formerly of Cape Elizabeth, Maine, had threatened Melissa Block and Guy Raz, hosts of "All Things Considered" in Washington, D.C., in January, authorities said.

Crosby appeared in District Court in Portland, Maine, on Friday and admitted to charges of sending threatening communications in interstate commerce and possession of a firearm by a felon, said Assistant Attorney Julia Lipez.

According to the indictment, Crosby contacted the two NPR hosts via the Internet from Portland on January 11. In messages to the hosts, Crosby threatened to rape, beat, torture and kill Block, and he called Raz an ethnic slur and also threatened his life, Lipez said.

When Crosby, 38, was arrested in Portland on January 26, investigators found a shotgun in his car, Lipez said. Because Crosby was previously convicted of state robbery and heroin possession felonies, he was barred from possessing firearms.

Crosby faces up to 10 years in prison and a $250,000 fine when he is sentenced. He has no known current address and he remains in the custody of the U.S. Marshal's Service. The FBI conducted the investigation against him.

Authorities notified NPR of all the legal proceedings against Crosby as required by the Victim's Rights Act, said Lipez.

Earlier this month, a fire broke out at the transmitter site of a National Public Radio affiliate in Arkansas and federal officials are investigating it as an arson, the manager of the station said.

NPR, which gets about two percent of funding from the government, has come under scrutiny in Washington this year as lawmakers search for ways to cut spending. House Republicans tried to cut or eliminate NPR's federal funding.

NPR chief executive officer Vivian Schiller resigned in March in the wake of a controversy sparked by a conservative group's video sting of an NPR official. The official was caught on tape making disparaging remarks about Tea Party supporters.

(Reporting by Zach Howard; Editing by Barbara Goldberg and Greg McCune)