Police said they were call shortly after 6:45 p.m. Monday to the 300 block of South Riverside Avenue for a report of a woman being groped.
Police said the 47-year-old woman was jogging along the Fox River Trail just south of the Illinois Street Bridge. While she was with a group, the others were head of her. She said she heard someone quickly approaching from behind and then a man put his arms around her shoulders, grabbing her chest and abdomen.
Police said the woman screamed at the man, who then fled west across a pedestrian bridge near Indiana Street, and then north on First Street toward Illinois Street.
Police said the suspect is described as a male with a thin build, approximately 5 ft. 6 in tall. He was wearing a gray or dark camouflage winter coat and dark pants.
If you have any information contact St. Charles police at 630-377-4435.