NEW YORK — An underground steam pipe explosion ripped through a street in Midtown Manhattan during rush hour Wednesday, killing one person from an apparent heart attack and injuring about 30 others.
The powerful blast spewed rubble into crowded streets, splashed mud on commuters, and sent a giant plume of murky hot steam billowing into the air.
Fears of a terrorist attack rippled across the city as the explosion shook buildings and sent terrified people fleeing down stairways and into the streets. The blast, which happened at 41st Street and Lexington Avenue near Grand Central Terminal, came from a broken 24-inch steam pipe that was installed in 1924, Mayor Michael R. Bloomberg said at a news conference.
"There is no reason to believe whatsoever that this is anything other than a failure of our infrastructure," Bloomberg said. "There is no reason whatsoever to believe that there is anything involved with terrorism or criminality."
Susan Del Percio, whose office is on the block where the explosion occurred shortly before 6 p.m, had been checking e-mail and preparing to leave work when she heard a thunderous boom. She noticed a plume of steam rising outside. It looked like thick smoke. Inside, it became dark, and when she looked at the windows again they were covered in a blanket of mud.
"The rumbling continued, and it was growling, and it got worse," she said. "All of the sudden you're like, 'OK, got to go.' "
She raced down 20 flights of stairs amid a crush of crying adults and children.
"We were all running, not looking back," she said. When Del Percio got outside, thousands of panicked people filled the streets. Steam wafted as high as skyscrapers. The air felt wet with mist and she noticed specks of mud splashing on her skin and clothes. She worried that a building might come crashing down. The experience brought back terrifying memories of Sept. 11.
"You are very much aware that you live in a targeted city," she said. "Is this another terrorist attack? It's something you think about."
The major concern for city officials Wednesday night was whether the area was contaminated with asbestos or other hazardous materials, Bloomberg said.
The city set up a "frozen zone," evacuating people within several blocks and warning anyone in the area to wash themselves, remove soiled clothes and put them in plastic bags, and close windows. Safety workers wore gas masks.
"If there was asbestos, the good news is with all the water generated by the steam, most of the asbestos was washed down," Bloomberg said, which may have resulted in "relatively little in the air."
At least three firefighters received minor injuries, and more than 20 other people were hurt, some seriously, Bloomberg said. The accident shut down subway lines, and caused brief panic among passersby.
Rain and thunderstorms pounded the area most of the day, and Bloomberg said the most likely cause of the explosion was "cold water getting into the pipe, and cold water apparently causes these to explode."
In 1989, a steam explosion in New York's Gramercy Park killed three people and sent a geyser of white-hot steam 18 stories into the air.
That blast, which blew out windows and showered buildings with asbestos, was caused by the condensation of water inside a steam pipe.
Some water mains in the city are 150 years old, Bloomberg said.
Steam pumps through mains beneath the city 24 hours a day, heating and cooling thousands of buildings.
There is always the danger of an explosion, the mayor added, but it is rare.
"We couldn't be prouder of how New Yorkers behaved in this incident," the mayor said.
People "helped each other, and [that's] exactly what you would expect," he said. "It's an inspiring thing for all of us."