NEW YORK — An 83-year-old steam pipe under a Manhattan street burst Wednesday, killing one person from an apparent heart attack and injuring about two dozen others.

The explosion sent rubble and steam flying through the air amid rush-hour commuters, shaking buildings and sending bystanders running for their lives.

The Daily News reported that a school bus operated by Pierce Coach Lines was caught in the blast, but the 15 children it had been carrying home from a day camp had been dropped off minutes earlier.

“As soon as the explosion happened, the driver and the matron jumped off the bus and ran as fast as they could,” Troy Pierce, director of operations for Pierce Coach Lines, told the Daily News. The explosion reportedly blew out windows and a door on the Type A bus.

While the blast evoked memories of the 9/11 attacks, city officials said that there was no indication of terrorism. “There is no reason to believe whatsoever that this is anything other than a failure of our infrastructure,” Mayor Michael R. Bloomberg said at a news conference.

The explosion also raised concerns of asbestos exposure. The city’s Department of Environmental Protection conducted tests and found no asbestos in air samples but did find some in debris and dust. Officials said that any brief exposures experienced during the incident were not likely to cause long-term health consequences.

A “frozen zone” comprising several blocks was set up to restrict access to the area, and clean-up efforts began Wednesday night.