NEW YORK (AP) – A titanic geyser of scalding vapor and earth erupted from a Manhattan street Wednesday when an underground steam pipe exploded near Grand Central Terminal, sending people running for cover as debris rained down on the street.

One person died, officials said. As many as 20 more were injured, at least four seriously.

The blast caused brief panic about another terror attack, with a scene eerily reminiscent of Sept. 11: people frantically rushing away from a Manhattan explosion and encountering chaos, debris and blaring sirens on the street. But officials quickly ruled out terrorism and said the blast was caused by a ruptured 83-year-old steam pipe.

Steam and dirt boiled from the ground for hours, generating a tremendous roar and spraying vapor as high as the top of the nearby Chrysler Building.

“I looked out the window and I saw these huge chunks that I thought were hail,” said Debbie Tontodonato, 40, a nearby business manager. “We panicked, I think everyone thought the worst, thank God it wasn’t. It was like a cattle drive going down the stairs, with everyone pushing. I almost fell down the stairs.”

The cause of the rupture remained under investigation. Bloomberg said the pipe, installed in 1924, might have exploded under extreme pressure caused by an infiltration of cold rainwater. It might have also been damaged by a water main break, he said.

“There is no reason to believe whatsoever that this is anything other than a failure of our infrastructure,” Mayor Bloomberg said at a news conference at the scene.

Authorities couldn’t immediately account for how the most seriously wounded victims sustained their injuries. Mr. Bloomberg said the person who died suffered cardiac arrest.

Many people were struck by falling chunks of asphalt or rock that had been blasted out of the ground. Mud covered some bystanders. A woman who was bleeding profusely was being helped by police while a man lay on a stretcher in the street.

Heiko H. Thieme, an investment banker in midtown, said the explosion was like a volcano.

“Everybody was a bit confused, everybody obviously thought of 9-11.”

When the steam cleared at nearly 8 p.m., a crater many feet wide was visible in the street. A red truck lay at the bottom of the hole. Two city buses and a small school bus sat abandoned in the middle of Lexington Avenue, covered with grit.

There were also concerns about what was spewed into the air. Some of the pipes carrying steam through the city are wrapped in asbestos.

“The big fear that we have is there may or may not have been asbestos release,” Mr. Bloomberg said.

He said he wouldn’t know test results until later, but he said if there was a release, it may have washed away with the water that came with the steam.
Con Edison head Kevin Burke said crews were working overnight to repair the damage. The pipe was carrying 150 pounds of pressure and the steam in the pipe was 200 degrees when it exploded.

He said officials were working to determine whether heavy rains from an earlier deluge that flooded parts of the city were to blame.

Sixteen people were taken to Bellevue Hospital, including the person who died, said spokesman Stephen Bohlen. Two seriously injured patients were being treated in the hospital’s trauma unit. The remainder suffered minor injuries, he said.

Two people were in critical condition at New York Weill-Cornell Medical Center, said hospital spokeswoman Emily Berlanstein.

City officials told residents to stay out of the area, and if anyone was exposed to the falling debris to wash with soap and water and place their clothing in a plastic bag. Area residents should close windows and use air conditioning.

“Normal precautions are what you should take. There’s no reason to panic,” Mr. Bloomberg said.

The scene was reminiscent of a similar blast nearly 20 years ago.

A steam pipe explosion near Gramercy Park in 1989 killed three people spewed loads of asbestos into the air – a fact that Con Ed later admitted it concealed for days while residents were exposed.

Ernesto Berdejo, who works the cash register at Pax, a restaurant in the area, said he saw people running and crying down the street Thursday. He and co-workers stayed in the street for about 20 minutes, then went back into the restaurant.

“We didn’t know what happened – something in the ground, really loud. We thought it was terrorism,” he said.

Millions of pounds of 400 degree steam are pumped beneath New York City streets every hour, heating and cooling thousands of buildings, including the Empire State Building.

The steam pipes are sometimes prone to rupture, however. The 1989 explosion sent mud and debris several stories into the air.

That explosion was caused by a condition known as “water hammer,” when water condenses in a closed section of pipe. The sudden mix of hot steam and cool water can cause pressure to skyrocket, bursting the pipe.

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Associated Press Writers Eric Vora, Richard Pyle, Tom Kent, Tom Hays, Marcus Franklin, David B. Caruso and Verena Dobnik contributed to this report.