Nassau County police are investigating after a group of men tied up the occupants of a Westbury home Friday night and ransacked the house.

An 11-year-old girl answered the front door of the home on Dover Street after hearing a knock at the door at 7:20 p.m., police said. A man wearing a black mask who was outside displayed a handgun and then forced himself inside the house.

Three more men in masks also entered the home and upon entering the kitchen, one grabbed a knife and held it to the neck of a 10-year-old girl, police said.

Both girls were forced into another room where a woman, 45, and a man, 35, were eating dinner. Police said the men bound the man’s hands with a belt and one of the masked men yelled “Where is the money?”

The men then ransacked the home, police said. They removed about $1,700 from a unoccupied basement apartment and before leaving, pushed a knife against the male victim while telling him not to call police.

The man suffered a small laceration from the knife; the victims called 911 after seeing the masked men flee through the backyard.

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Police said the masked men are described as about 5-foot-6, weighing 160 to 170 pounds and wearing all black clothing.

The male victim received medical treatment at the scene.