Thick gray smoke billowed out of the 191st Street No.1 train station in Manhattan's Washington Heights on Tuesday afternoon.
FDNY Deputy Assistant Chief Mike Woods said the train hit "some kind of piece of equipment," as it entered 191st Street subway station, which then made contact with the third rail and created a smoke condition.
Eighteen people reportedly had minor injuries and were evaluated on scene.
Two people refused medical attention, and 16 people were taken to area hospitals.
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Emergency responders assessed nine patients, all suffering from smoke inhalation.
Woods confirmed there were minor smoke inhalation-type injuries but were assessed by EMS.
Despite the heavy smoke, Woods said there was "no active fire in the train."
The fire was put out and subway service was temporarily suspended in both directions between 145th Street and 215th Street.
Trains are running on severe delays in both directions after a rail was replaced at 191 Street.
Authorities do not believe anyone was responsible for leaving the object on the tracks, but transit officials will continue their investigation.