Times Square could have seen a "huge thermal ball" rising 30 to 40 feet in the air and causing "several hundred casualties" if the explosives packed into a Nissan Pathfinder left parked there detonated, an international bomb expert said Monday.

"Had that detonation functioned correctly, we would have seen a huge explosion," said Kevin Barry, chairman of the board of advisers of the 5,000-member International Association of Bomb Technicians and Investigators.

The explosion would have singed Times Square and blown out windows of buildings, but would not have been strong enough to bring down any surrounding buildings, said Barry, a former supervisor with the NYPD bomb squad.

The inferno would have lasted only "a few seconds" as the fuel would quickly be burned up, he said. But the level of catastrophe, from the propane tanks "had they exploded in this intersection, would have caused several hundred casualties," mostly from burns and fragmentations.

"The problem with a thermal ball like that, when it encapsulates people as it goes out, people inhale it and then we get lung damage and burns, and you get thermal burns of the skin, face, hair. So this would have been a real horrific scene."

Asked how close New York had come to disaster, Barry said, "We came within a millisecond."

Other experts agreed with his description of the potential explosion, though they said faulty construction of the bomb including the detonator made it unlikely it would have gone off.

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It "would have been quite an explosion," said Jerome Hauer, former head of New York City's Office of Emergency Management. "Not an Oklahoma City type, but enough to have caused damage to some buildings and to have injured and killed a number of people, particularly with the density of people in Times Square on a Saturday night."

Still, he cautioned, "this was not a millisecond away. That's a bit too dramatic" because of the unlikelihood of the bomb exploding. "If this was an international group, it was an international group of morons."

With Bart Jones