HELENA, Mont. (AP) — Federal prosecutors say a North Carolina man has pleaded guilty to sexually exploiting two Helena girls by coercing them to send nude photographs of themselves.

Theodore Castine of Mooresville, N.C., pleaded guilty Wednesday to two counts of sexual exploitation of children.

Prosecutors say the 54-year-old Castine contacted a 14-year-old Helena girl via Facebook and text messages demanding she send him pictures or that he would find her.

The girl sent the pictures and contacted authorities, who took over the girls' accounts, identified Castine and arrested him.

Authorities found pictures of another Helena girl in Castine's email account. Prosecutors say Castine coerced her in a similar fashion.

U.S. District Judge Charles Lovell set sentencing for Sept. 27.

Castine faces between 15 and 30 years in prison and a possible $250,000 fine.