BANGOR — The Englishman charged photographing his sexual assault on a 13-year-old Levant girl met online in a Harry Potter chat room waived indictment and pleaded guilty Friday to one count of production of pornography.

Nicholas Cheese, 26, of Oxford, England, faces a mandatory minimum of 15 years in prison and a maximum of 30 years. He also could be fined up $250,000. A sentencing date has not been set.

Cheese will be held without bail at the Penobscot County Jail pending the resolution of his case.

He initially was charged July 1 with one count each of gross sexual assault, a Class A felony, and sexual exploitation of a minor, a Class B felony, according to a previously published report. Those charges were dismissed by the Penobscot County District Attorney’s Office in September when Cheese was charged in federal court.

Cheese came to the attention of law enforcement June 30 when the girl’s parents reported she had been sexually assaulted by a 26-year-old man from England, according to an affidavit filed in U.S. District Court. In an interview with a detective from the Penobscot County Sheriff’s Office, the girl said she met Cheese online in April or May 2012.

According to the prosecution’s version of events to which he pleaded guilty, Cheese told the girl he was coming to Texas for a convention and would stop in Bangor to see her. The two met at Cheese’s motel room June 26, 27 and 28, when he assaulted her.

When interviewed by investigators, Cheese admitted that he knew the girl was 13, that he had traveled to Bangor to have sex with her and that he had previously asked the girl for nude photos and videos. Those and at least one sexually explicit photo taken in Cheese’s motel room were found on his cellphone and iPod, according to court documents.