It happened just after 10 a.m. at Broadway and West 225th Street in Marble Hill, with the manhole cover blasting into the elevated subway line above.
There was concern that the explosion may have compromised the tracks of the 1 train, but a survey found no structural damage outside of a dent in a beam that did not impact service.
The injuries were described as minor, and one person was transported to a local hospital.
Related: Manhole explosions, fires awake residents on Upper West Side
An electrical fire is believed to be the cause of the explosion.
The FDNY and Con Edison responded, and crews remain on scene.
There were no reported power outages in the area.
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