By Emanuella Grinberg

PHILADELPHIA (CNN) –Members of the New York Police Department bomb squad are investigating the cause of an explosion in Central Park on Sunday that nearly blew a man’s leg off, police said.

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Preliminary investigation suggests the explosion was an “experiment with fireworks or homemade explosives,” NYPD Deputy Chief John O’Connell said at a news conference Sunday afternoon.
“We do not have any evidence of a constructed device or commercial-grade fireworks,” he said. “There are no specific or credible threats directed at New York for July Fourth.”

The victim was identified as an 18-year-old tourist from northern Virginia. He was visiting the park with two friends, ages 18 and 20, O’Connell said.

Shortly before 11 a.m. the three young men jumped off a rock in the park, triggering the explosion that left one of them injured.

Witnesses said the sound of the blast rippled through the park like a “cannon,” scaring birds off trees.

The victim was transported to Bellevue Hospital in serious but stable condition, where he is undergoing surgery. The victim and his two friends are not considered suspects, O’Connell said.

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Evidence suggested the work of an amateur hobbyist, who are known to experiment with explosives during the July Fourth holiday, NYPD bomb squad commanding officer Mark Torre said.

He estimated that the explosive had been in the park for longer than a day. Evidence suggested it was not meant to go off from someone stepping on it, Torre said.

Witnesses and victims consented to police searches of their homes and cars, the NYPD said. Nothing was found.

Explosive material from the scene is being tested at a bomb lab, a federal law enforcement official told CNN. Members of the FBI-led Joint Terrorism Task Force with expertise in explosives are assisting given the nature of incident, the official said.

Another law enforcement source told CNN the explosive material was contained in a plastic bag.

The park remained open except for the area where the incident occurred.

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