The fire started shortly after noon Thursday inside 333 West 33rd Street between 8th and 9th Avenues.
A total of 28 patients were being treated on scene with minor injuries including six firefighters with minor injuries.
West 33rd Street was closed to both pedestrians and vehicular traffic between 8th and 9th Avenues, but had reopened Thursday evening.
The building remained closed for the rest of the day.
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