DENVER (KUSA) - A man in a thong has been running around, exposing himself and terrorizing neighborhoods around Sloan's Lake, Colorado.

"We're looking for an individual who we have titled the 'Thong Bandit,'" District 1 Commander Paul Pazen said. "He is fully clothed somewhere in the mouth of an alley, will disrobe down to a thong and expose himself further in front of female citizens in northwestt Denver."

Pazen says the man was first seen at the end of the summer, and has been quiet for several months, but there have been four reports of him exposing himself again in the last two weeks: once on Feb. 17 and Feb, 18th. Denver Police have assembled teams of officers to look for this man.

"It's a crime to expose yourself to folks," Pazen said. "We need to make sure that he doesn't take that next step."

The underwear color has changed over time, police tell 9NEWS. Initially they were looking for somebody wearing a pink thong, most recent report indicate the thong is now black, or a dark color.

Police have a description and a sketch that took a while to get.

"It's really difficult for people to process what they see in something like this [case]," Pazen said. "This is not something that is typical behavior, and it was difficult for us to get somebody that detailed enough information of this person's face in order to help us with the sketch."

Detectives are looking for a white or a Hispanic man, in his 20s or 30s. He has black or darker-colored hair, with an athletic built, and is approximately 5 feet 7 inches to 6 feet tall.

One reason it's taken a while to catch this guy, police say, is people don't report seeing him right away. One woman, Pazen said, saw the man on her way to work but called police after she came home. Police say it's really important people who see the man to call them immediately.

"If you see this individual disrobing or putting clothing on [in] an alley, and you can do it safely, we'd always ask you call 911 first, and if you have the ability to utilize the camera on the smart phone that would aid us greatly identifying this individual for future apprehension," Pazen said.

For now, police are using predictive analysis, trying to figure out where this guy is going next.

"We look for patterns - day of week, time of day, weather conditions - to see if we could guess when an individual will try to perpetrate a crime," Pazen said. "It's very difficult to try to guess what a human being is thinking, and here, those challenges are even greater when you have somebody who thinks it's OK to run around in a thong."

If you have information that leads to an arrest and charges, you could be eligible for a cash reward. Call CrimeStoppers at 720 913 STOP to report him.