SACO – Saco police arrested a partially clothed Biddeford man on a sex charge after he allegedly grabbed a police detective through his clothing.

Luis H. Lopez, 51, was charged with unlawful sexual contact following the Thursday incident on a trail in a wooded area near Mill Brook Road, according to police.

Since early summer, Saco police have stepped up patrols and charged several men with a variety of crimes, including indecent conduct, assault and unlawful sexual contact, in an effort to stop illegal activity on the city’s walking and hiking trails.

On Aug. 22, Detective Ken Foss was checking Mill Brook Road when he saw Lopez allegedly engaged in suspicious activity, according to police. Lopez was not wearing a shirt and had his pants down when Foss saw him on the trail, Police Chief Brad Paul said in a news release.

Lopez allegedly gestured for the detective to come closer, then reached out and grabbed Foss through his clothing, Paul said.

Lopez was arrested and released after posting bail. He is scheduled to appear in Biddeford District Court on Sept. 25.

Paul said his department will continue their efforts to stop illicit behavior “until the issue ceases to be a problem” for users of the city’s trail system.