SPARTA, Mich. - Prosecutors have filed criminal charges against a Sparta, Michigan man after investigators said he performed circumcisions on adult males without a license.

Thomas Heugel had a "a makeshift operating room in his house," according to a Kent County sheriff's lieutenant.

"He quite often wore a doctor's uniform that really left the impression he was a medical doctor," Lt. Kevin Kelley said on Wednesday.

Investigators believe the circumcisions were the only medical procedures Heugel was performing.

The 56-year-old was able to attract clients through postings on Craigslist, an online classifieds site, and Adam4Adam, an online personals site, according to investigators.

Heugel faces a charge of unauthorized practice of a health profession and a separate charge for performing massages and body piercing without an occupational license.

As he left the Kent County jail Wednesday evening, Heugel did not respond to requests for comment.

Investigators have found three victims, the lieutenant said, but believe there are "many others."

Kelley asks anyone who had a medical procedure performed by Heugel to contact the sheriff's department.

"We really don't know what his motives were and we continue to investigate," Kelley said. "Hopefully, as more victims come forward, we'll be able to get the answer to some of these questions."