The Ames Police Department's investigating the overnight armed robbery of a west side convenience store. Lt. Dan Walters says the Swift Stop store at 3406 Lincoln Way was held up just before 4:00 A.M. Walters says the suspect showed the store's clerk a gun taking cigarettes and an undisclosed amount of cash. A preliminary description of the suspect is of a black or Hispanic male wearing a mask over his face and a black hooded sweatshirt. This is the same convenience store that was robbed back in November.