NIAGARA FALLS – A rash of armed robberies has hit the city over the past two months, with one gas station being held up three times.

Police are investigating at least six reports of robberies, involving one or two men armed with weapons demanding cash from gas station convenience stores.

In most cases, the robbers wore masks and were armed with guns, but in one case the robber displayed a knife. In another, a man shielded his face with a hooded sweatshirt.

City of Niagara Falls Police Detective Lt. Michael Trane and Police Superintendent E. Bryan DalPorto both said they don’t believe the robberies are related.

“There doesn’t appear to be a pattern,” DalPorto said.

Trane said they are still investigating.

The most recent armed robbery was reported just after 11 p.m. Sunday.

Armed with a rifle, a knife and a handgun, two men wearing white masks, black hooded sweatshirts and gloves robbed a Sunoco gas station and convenience store in the 900 block of Pine Avenue on Sunday night, according to police.

The store clerk said he was counting money when the two men came in and demanded that he open the register.

He said one man pointed a handgun at him while the other, armed with a rifle, ran behind the counter.

The clerk said the man with the rifle shot at the floor. The clerk said that after hearing the shot, he opened up the cash drawer and handed over all of the cash inside – about $150. The men then fled down an alley behind the store, according to police.

A witness told police he heard the shouting and the shots and called 911. Police secured a surveillance video, and the city detective bureau is now investigating the case.

In the previous cases, armed gunmen robbed a 7-Eleven in the 6500 block of Buffalo Avenue on Feb. 4.

A Valero gas station in the 4700 block of Hyde Park Boulevard was robbed twice in February, once at gunpoint and another time at knifepoint, and then hit a third time at gunpoint March 6.

Also, a Sunoco gas station in Sanborn was robbed at gunpoint March 7.