Nassau County Fire Marshal Vincent McManus says two firefighters were in serious condition, while the other three were expected to be released from the hospital shortly.
The fire broke out at a house in Long Island's New Hyde Park shortly before 1 p.m. Friday. McManus says the firefighters were carrying a hose into the basement of the home when a burst of flames erupted.
Three of the firefighters escaped up the stairs. One climbed out a basement window and the most seriously injured was rescued by colleagues.
An elderly resident and a home health aide escaped uninjured.
The New Hyde Park Fire Department responded to the scene along with nine other local volunteer fire departments. There were one hundred and twenty volunteer firemen at scene.
The Arson Bomb Squad and the Nassau County Fire Marshal are investigating.