Investigators have determined that a holdup at a Subway fast-food restaurant in Carle Place on Tuesday is the fifth such type of knifepoint robbery tied to the same suspect, police said Wednesday.

Nassau County police said the pattern robberies have taken place over a six-week period, all committed by a man who uses either a knife or machete as his weapon of choice.

The Subway robbery occurred at 5:53 p.m. at the sandwich shop on Old Country Road, police said, with the robber last seen headed north on Cherry Lane after running off with the money.

The suspect had a dark scarf covering his face and wore gloves, police said. He was described as stocky, about 5 feet, 8 inches tall and wearing a dark, waist-length jacket and light-colored cargo pants, police said.

A man who identified himself as the manager told News 12 Long Island that he was with a colleague when the man entered the store, “and he says he has a big knife and he told me ‘give me that money, give me that money’ and I said OK, just relax.’ ”

The announcement that the Subway robbery is part of the continuing pattern comes two days after Nassau police highlighted another robbery in the crime pattern: a knifepoint holdup at a Westbury Carvel on Sunday. Investigators said the same suspect also tried to rob a Seaford Dunkin’ Donuts on Feb. 15, then held up a South Farmingdale Carvel the same day, before orchestrating a holdup at a Bethpage Carvel on March 21.

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In each incident, the suspect had his face covered or wore a mask, police said. He carried a machete in the first three crimes, and detectives are trying to determine why he switched to a knife in the Westbury robbery, police said.

Police said they are on “high alert” for the serial robber, directing patrol and specialized units to places where businesses similar to the ones hit are located.

Detectives ask anyone with information to call Nassau Crime Stoppers at 800-244-8477. All calls will remain confidential.

CORRECTION: The robbery suspect was last seen walking north on Cherry Lane. An earlier version of this story misstated the name of the street because of incorrect information provided by police.