The explosive that severely injured a man in New York's Central Park today was likely "an experiment with fireworks or explosives," but did not seem like a device made deliberately to hurt anyone, officials said.
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It was still not clear exactly what the explosive was, but police said they did not believe it was connected to terrorism.
Mark Torre, commanding officer of the NYPD bomb squad, added that investigators are leaning toward considering this the work of an explosive "hobbyist," an amateur or someone who knows chemistry.
It could have even been some sort of "experiment" that was not meant to explode, as it did, when stepped on, Torre said.
Three men were walking in an area of the park not far from the entrance to the Central Park Zoo when the explosion occurred, severely injuring the foot of one of them, a New York Police Department spokesperson said.
Police identified the victim as an 18-year-old, and said his friends were interviewed, but they were not suspects, nor were they injured in the explosion.
The injured man was taken to Bellevue hospital with a "possible amputation," a Fire Department of New York spokesperson said. He was in serious but stable condition, officials said early Sunday evening.
One of the young men, Thomas Hinds, 20, said the explosion was "definitely not a firecracker." He said his friend, whom he identified as Connor Golden, 18, had his foot "severely mutilated" by the explosion.
"We were climbing down the rocks, Connor was 6 feet behind me and all of sudden I felt the explosion on my back," Hinds said. "The explosion sounded like a gunshot next to my ears. I turned around and saw his foot which wasn’t completely blown off but was severely mutilated. My other friend Matthew [Stabile, 18] was behind Connor and all he saw was a massive amount of dirt go flying up in the air. My understanding, I could be wrong, is he’s in surgery right now and they are hoping to keep his foot."
He said police questioned them separately and "were understandably going at us hard asking about firecrackers because the idea that there would be some sort of bomb in Central Park is really scary."
The NYPD bomb squad was on the scene, and a portion of the park was closed for the investigation, police said.
ABC News' Aaron Katersky contributed to this report.