ST. LOUIS • A 78-year-old West Virginia man faces a federal charge after traveling to Troy, Mo., to have sex with a teenage boy, criminal court documents say.

Jack E. Gravenmier, of Charleston, was arrested Saturday morning by the FBI and appeared in court Monday. He has a detention hearing today, as prosecutors are seeking to have him held in jail until trial.

Gravenmier met the 14-year-old boy last year and the two had a sexual encounter, documents claim. After the boy's mother alerted police last month, investigators took over and began corresponding with Gravenmier as if they were the boy, according to an affidavit filed in federal court here by James A. Stewart. Stewart is a member of the Troy police and the St. Charles County Cyber Crime unit and was posing as the boy.

Gravenmier sent Stewart what appears to be child pornography, including images that he claimed to have taken, and reserved a room at the Troy Super 8 motel for Feb. 11 and 12, Stewart wrote.

Gravenmier promised to bring two memory cards with images and video of child pornography, soiled women's underwear, a sex toy and $100, he wrote.

Gravenmier is now charged with attempting to persuade a minor to engage in sexual activity, but Lt. Chris Mateja, head of the Missouri Internet Crimes Against Children Task Force, said that he anticipates additional charges will be filed, including production of child pornography. Mateja said Gravenmier boasted of taking some of the photos.

Mateja said that Gravenmier is a retired chemical engineer.

His lawyer could not be immediately reached for comment.