Two days after a man was arrested for allegedly running naked through the Cascade Brook trail system in Saco, police arrested another man there, this time on a charge of unlawful sexual contact.

An undercover officer was walking on the trails Thursday, part of stepped-up patrols after police received complaints about “suspicious activity and illicit behavior” in the park. The officer encountered Allen Hahn, 64, of Old Orchard Beach, on a trail just before 1:30 p.m. Thursday. After a brief conversation, Hahn stepped toward the officer, grabbed the officer’s genitals though his clothing and said “Are we doing this?” police said.

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Hahn was charged with unlawful sexual contact and assault, police said. He was released on $500 bail and is scheduled to appear in Biddeford District Court on July 10.

On Tuesday, police charged a Yarmouth man with indecent conduct after he was spotted walking naked on one of the trails by Chief Brad Paul. The man ran but was apprehended when he stopped to put on his pants.

Deputy Chief Jeff Holland said the Cascade Falls park has become a popular destination for residents and visitors because of the recently improved trail system, and scenic waterfalls. But police also have received complaints that it has become a meeting place for men.