Waltham Police are investigating an armed robbery at a Lake Street conveience store on Thursday, Dec. 6.

The incident started at 9:42 p.m. when police received a report of an armed robbery at Lakeview Convenience at 225 Lake St., according to Waltham Police Sgt. Joseph Guigno. 

A man dressed in a black jacket, dark pants and a white facemask entered the store and demanded $50 from the clerk and displayed a knife, Guigno said. He then reached over the counter and forced the register open and stole an undisclosed amount of cash, Guigno said. He fled the store on foot.

Police responded and set up a perimiter and dispatched a K-9 unit, Guigno said. The dog tracked a scent to the area of Pine Hill Circle where he found the suspect's clothes, including a jacket, shoes, pants, masks and gloves. Police were unable to locate the suspect. 

Police are investigating the incident. The clerk was not injured.