(STMW) — Police are warning people about an attempted sexual assault that happened Saturday in north suburban Evanston.

A 23-year-old woman was walking in the 1300 block of Maple Avenue about midnight when a man knocked her to the ground and tried to undress her, Evanston police said in an alert issued Monday.

The man kept attacking the woman when she tried to defend herself, police said. She was later treated for facial injuries at a local hospital.

The attacker is described as a man of an unknown race, with fair skin and a slim build, police said. He was about 5-foot-7 to 5-foot-8, and wearing blue jeans and a dark coat. He may have also been wearing a knit cap, police said.

The suspect was seen just before the attack walking eastbound on Dempster Street near Maple Avenue, and was not in custody as of Monday evening, police said.

No similar incidents have recently been reported to Evanston police.

Anyone with information should call (847) 866-5000 or send a text message with an anonymous tip to 274637, with the words “EPD Tip.”

(Source: Sun-Times Media Wire © Chicago Sun-Times 2013. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed.)