A mechanical failure sparked two small blazes on the track beneath the train at around 10:30 a.m., leaving it stranded below Archer Avenue in Jamaica between the 121st Street and Sutphin Boulevard stations.
About two dozen passengers climbed out and walked on the tracks to the 121st Street station, which is above ground, before help arrived, officials said.
Some 80 firefighters and transit workers used an emergency train to link up with the disabled cars and evacuate more than 350 trapped passengers. It was not known last night how long the passengers were stranded.
One passenger was taken to a hospital for an asthma-related illness.