JEFFERSON COUNTY, Colo. - A woman was attacked while walking on a south Jeffco bike path Friday morning.

The path, near C-470 and Wadsworth Blvd., includes a tunnel where it goes underneath C-470. When the woman entered the tunnel,  she was attacked and sexually assaulted.

The suspect is described as a white male, 30 to 40 years old, 5 feet 7 to 5 feet 9 inches tall, weighing 175 to 185 lbs, with a lanky and athletic build. He had tan skin and light brown hair. Sheriff's deputies told 7NEWS he was wearing bike clothes at the time.

"The fact that this happened in daylight, first thing in the morning is stunning," said Mark Techmeyer, a spokesperson for the sheriff's department. "It has us concerned, we want to get our hands on this guy real quick."

The Jefferson County Sheriff’s Office had bike patrol deputies on the bike trail Saturday,  handing out flyers with a composite sketch of the suspect. Deputy Josh Garcia said they hope to gather leads by talking with people who use the path regularly.

"The person is definitely someone who frequents the area, does a lot of trail walking. He has been seen by the victim at least in the last couple months," Garcia said.

Meanwhile, people who live nearby told 7NEWS this is unusual.

"It's really quiet down here. There's usually so many people with their dogs out and everything else, nothing like that happens," Robin Fries said.

If anyone recognizes this man, or has any information regarding this crime, they are asked to call the Jeffco Sheriff’s Office tip line at 303-271-5612.