A small fire in a child’s empty bedroom sent about 100 New Cassel residents rushing out of a three-floor complex in an evacuation that injured three police officers trying to get people out Thursday night, authorities said.

The flames in the bedroom on Prospect Avenue were put out in minutes by the fire sprinklers, the fire alarms worked and elevators were automatically shut down as required, but one side of the double front doors was screwed shut, said Michael Uttaro, Nassau County assistant chief fire marshal.

“The biggest issues were the smoke and trying to evacuate people out of the building,” he said.

The fire marshal’s office issued several citations to the owner, including for the locked front door of the complex, which has scores of apartments above ground-level stores.

The fire started about 6:50 p.m. and appeared to be an electrical malfunction, according to the fire marshal’s office.

The first responders to arrive, Nassau police officers, knocked on doors and escorted people down the stairs, Uttaro said. That included several people in wheelchairs, he said.

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Three officers suffered minor smoke inhalation and were taken to the hospital, Uttaro said.

The fire investigator praised the officers, saying “They did a great job.”

Authorities said the county Office of Emergency Management took about 75 people by bus to the nearby Yes We Can Community Center, which is run by North Hempstead Town. Uttaro said others left to find their own shelter.

County Executive Edward Mangano and North Hempstead Supervisor Judi Bosworth were at the scene, Uttaro said.

About 50 firefighters from Westbury, Hicksville, Carle Place and Jericho responded to the scene, he said. The town building department officials were still at the scene late Thursday to assess conditions before allowing residents to return, Uttaro said.

CORRECTION: An earlier version of this story misstated the community where the apartment complex is located.