A convenience store in Shirley was robbed by a man with a knife Tuesday morning, but it was not believed to be linked to a series of 16 other knife point robberies across Long Island in the past two months, Suffolk County police said.

The 7-Eleven store at 228 William Floyd Pkwy., a stand-alone store next to a small shopping center near Brushwood Drive, was robbed at 1:50 a.m., police said.

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A man with a knife entered the store, demanded cash and fled with an undetermined amount of money, Suffolk County police said.

“Major Case Unit detectives do not believe that this robbery is part of any established pattern,” Assistant Police Commissioner Justin Meyers said in a statement.

Since mid-February, the robber is suspected of hitting 16 stores — 10 in Nassau and six in Suffolk, mainly chain ice cream shops and sandwich stores, according to police. Two of those were attempted robberies. No injuries were reported in any of the incidents.

All but one of the robberies have occurred roughly between 6 p.m. and 10 p.m. The outlier was a 1:50 p.m. robbery of a grocery store in West Babylon.