Nassau police are investigating an armed robbery of a 99-cent store in Levittown, police said Monday.

The robbery occurred Sunday about 7:21 p.m. when an unidentified man entered the Island 99 Cent Store at 3025 Hempstead Tpke. and said he had a gun and demanded money, police said.

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A store employee, a 33-year-old woman, handed over an unknown amount of cash, police said. The robber also took the victim’s cellphone and fled on foot.

The robber is described as a man as about 5 feet, 4 inches to 5 feet, 6 inches tall, with a thin build, and wearing a gray mask, a gray hooded sweatshirt, dark colored jeans, black sneakers, black gloves and a black jacket, police said. No injuries were reported, police said.

Detectives asked anyone with information about this crime to call Nassau County Crime Stoppers at 800-244-TIPS. All callers will remain anonymous.