The fire was caused by electrical problems, which cut power and prompted the dismissal, officials said.
A call came in from the school at 9:47 a.m., police Lt. Robert Koziak said. "There was a smoke condition in the boiler room. We responded and the situation was under control."
There was a small electrical fire related to the power outage due to the fallen power lines on West Boston Post Road, said Debbie Manetta, director of public information for Mamaroneck Schools.
All students and personnel were safely evacuated, Manetta said. After the fire department inspected the building and indicated it was safe to return, everyone went back into the building.
The 11 a.m. dismissal was due to the continued power outage. Manetta said she did not have information on when power would be restored.
One custodian was evaluated on site for smoke inhalation but refused medical attention, Koziak said.
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