NEW YORK (AP) — Police in New York say a firework that exploded and injured a 19-year-old who stepped on it in Central Park probably was created by someone with a basic knowledge of chemistry, but not designed to intentionally hurt people.

The injured man, who police didn't identify, was walking in the park with two friends Sunday when he stepped on a rock covering the explosive. His left foot was seriously injured and he was to undergo surgery at a hospital.

The blast on the east side of Central Park could be heard for blocks, leaving some with the belief that it was part of a July Fourth celebration.

Lt. Mark Torre, of the New York Police Department's bomb squad, says the firework was like an "explosive experiment" probably was designed to "make a large noise."

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