The unidentified man was walking in Central Park with friends, he stepped on a rock, there was some sort of explosion and he injured his left foot.
A 19-year-old man was seriously injured, and may have lost a foot, after a small explosion in New York's Central Park on Sunday, authorities said.
It was unclear what caused the explosion but it may have been fireworks ahead of the Independence Day holiday on Monday.
The incident also comes as US authorities step up security over the holiday weekend, especially at airports and other transport hubs.
The unidentified man "was walking, he stepped on a rock, there was some sort of explosion and he injured his left foot," New York Police Sergeant Lee Jones told AFP.
He was taken to a hospital in critical but stable condition.
The incident took place around 11:00 am (1500 GMT) at the huge park in Manhattan.
Jones said the man was walking in Central Park with friends, and may have been from out of town.
An FDNY spokesman said first responders had transported the man "with a possible amputation to his leg... It appeared to be partially amputated" by the explosion.
NYC Health + Hospitals/Bellevue did not immediately respond to a request for comment.