The Subway shop robbed by a knife-wielding robber Monday was hit again Friday, and detectives want to see if the suspect is one of the serial criminals who are preying on Nassau businesses, police said.

A male with a white mask demanded money from an employee at the New Hyde Park location shortly after 9:10 p.m., Nassau police said. Preliminary reports that he may have had a knife were not confirmed, police said late Friday.

No one was injured, police said.

Nassau police have had their hands full this year with three pattern robberies involving suspects with knives.

The robber declared “priority No. 1” by Nassau police has struck at least a dozen times, hitting primarily Dunkin Donuts but also Carvel and Subway stores, mostly around closing time, when fewer people are around, police said.

He is the one who robbed the New Hyde Park Subway just before 10 a.m. Monday, police said.

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A second robber has targeted Valley Stream area businesses, taking the entire cash register with him, police said.

The third is believed to have hit the same Williston Dunkin Donuts twice this month. He was heavyset, wore a white-hooded sweatshirt and a mask, which in one case appeared to be a light-colored surgical mask, police said at the time.

It’s not clear if the Subway shop robber is the same culprit in the Williston Dunkin Donut cases.

Authorities encourage anyone with information to call Crime Stoppers at 800-244-8477.