BANGOR, Maine — A 19-year-old from Maine who the FBI says built homemade explosives and plotted to attack a mosque in the name of the Islamic State group will plead guilty to providing material support to terrorists.

Xavier Pelkey of Waterville faces a maximum of 15 years in prison under a plea agreement in which a second charge will be dropped, according to court documents filed Wednesday. The change-of-plea hearing is set for next week in U.S. District Court.

Pelkey’s attorney did not immediately respond to a phone message seeking comment on Thursday.

Law enforcement officials said Pelkey was in communication with two juveniles — one in Canada, the other in Illinois — about conducting a mass shooting at a Shiite mosque in the Chicago area and possibly other houses of worship. All three alleged plotters believed in a radical form of Sunni Islam that views the Shiite branch of Islam as nonbelievers, officials said.

Pelkey was 18 when he was arrested last year by FBI agents who found three homemade explosives in his residence. The devices were made of fireworks bundled together with staples, pins and thumb tacks to create shrapnel, the FBI said.

Investigators also found a handwritten document in Pelkey’s bedroom that appeared to be a draft statement about the planned mosque attack, claiming it in the name of the Islamic State group. In the statement, Pelkey claimed allegiance to the extremist Sunni militant group, and an IS flag was painted on the wall of his bedroom, investigators said.

Despite their defeat in Syria in March 2019, the militant group’s sleeper cells still carry out deadly attacks in both Syria and Iraq where they once declared a “caliphate.”