A man who filmed himself sexually assaulting young Asian girls pleaded guilty to child pornography charges.

William Constable, 54, a self-employed contractor, was arrested in October when he tried to retrieve a camera he left in a Cape Cod, Massachusetts, hotel room. A hotel employee who found the camera called police after seeing images of a man having sex with young girls.

Prosecutors said the camera and dozens of cassettes and compact discs later seized from Constable's Nantucket home showed him sexually assaulting girls as young as 5, sometimes two at a time.

During a hearing Tuesday in U.S. District Court, Constable pleaded guilty to seven counts of sexual exploitation of children and one count of possession of child pornography. According to a plea agreement filed with the court, the recommended sentence will be 25 years in prison and a $50,000 fine, with restitution to be determined when Constable is sentenced on June 10. He also faces lifetime supervision after his release.

Constable told investigators he videotaped himself having sex with the girls so that he could later "re-create the moment," Assistant U.S. Attorney Dana Gershengorn said.

A review of Constable's passport showed that since 1993, he visited Thailand, Cambodia and Vietnam every year except one, Gershengorn said. Constable told police he had sex with about 30 underage girls in Asia.

When first questioned by police, he said the girls were between the ages of 12 and 17, but later admitted some of the girls were as young as 7. Authorities who viewed the videos believe the vast majority of the girls were under 12, with some as young as 5, Gershengorn said.

Constable did not speak at the hearing, except to admit the allegations recited by the prosecutor and to enter guilty pleas. He faces a mandatory minimum of 15 years in prison on the sexual exploitation charges.

Gershengorn said the FBI has been working with U.S. Customs and Immigration Enforcement and Asian authorities to try to identify the girls in the video clips.