ROCHESTER, Minn. (AP) âÄî Workers at the Mayo Clinic in Rochester have been alerted after a 28-year-old female employee was attacked in a stairwell. Police say the woman was struck in the head by an unknown man in a public stairwell used primarily by employees and the not the public. The woman was not sexually assaulted. Police Capt. Brian Winters says investigators don’t know what the woman was hit with, but she did suffer minor head injuries Tuesday afternoon. She didn’t need hospitalization. No description of the suspect is available because she was attacked from behind. The man made no demands and fled after the attack. Mayo Clinic Adam Brase says it notified all of its staff of the incident and offered them safety tips. Rochester police are investigating. ___ Information from: Post-Bulletin, http://www.postbulletin.com