Prince William County police are searching for a man who allegedly sexually assaulted a motel clerk Wednesday night in Woodbridge.

A 33-year-old female clerk got a call to let someone into a room at the Econo Lodge at 13317 Gordon Blvd. around 10:15 p.m., police said. When she started walking to the room, police say, a masked man forced her into a room with a knife. The victim was then allegedly knocked unconscious and sexually assaulted.

There was no one staying in the room to which the clerk was called, police say.

No further description of the man was provided to police, who are continuing to investigate..