New York: A college student from Fairfax, Virginia, was seriously injured on Sunday in New York City's Central Park when he unwittingly jumped on explosive material that had been left next to a rock, according to police and his family.

The bizarre accident forced the amputation of 18-year-old Connor Golden's left leg below the knee and set the nation's largest city on edge a day before the July 4 holiday was expected draw thousands to watch the city's annual fireworks display.

The injured tourist is carried to an ambulance in Central Park in New York on Sunday. Credit:AP

New York City police officials said at an evening news conference that they had no evidence to indicate the blast was related to terrorism and had documented no credible threats against the city. But many questions about the case remain unanswered.

Deputy Police Chief John O'Connell said the explosion occurred near East 60th Street and 5th Avenue shortly after 10.50am. Golden and two friends jumped off a rock and Golden landed directly on the explosive material. A New York City Fire Department spokesman said the blast nearly blew off Golden's foot, but his two friends were uninjured.