An underground steam pipe explosion tore through a Manhattan street near Grand Central Terminal on Wednesday, swallowing a tow truck and killing one person as hundreds of others ran for cover amid a towering geyser of steam and flying rubble.
New York Police Department spokesman Paul Browne said the explosion was not terrorism.
"There is no reason to believe whatsoever that this is anything other than a failure of our infrastructure," Mayor Michael Bloomberg said at a news conference at the scene of the blast.
The mayor said a 24-inch steam pipe installed in 1924 broke, with the explosion most likely caused by the introduction of cold water into the pipe.
Eighteen people were taken to local hospitals, including the person who died, said spokesman Stephen Bohlen. He said two seriously injured patients were being treated in Bellevue 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 spokeswoman Emily Berlanstein.
Initial burst taller than Chrysler Building
A plume of steam and mud shot from the center of the blast, generating a tremendous roar. The initial burst of steam rose higher than the nearby 77-story Chrysler Building, one of Manhattan's tallest buildings. The air near the site was filled with debris.
Heiko H. Thieme, an investment banker, had mud splattered on his face, pants and shoes. He said the explosion was like a volcano. "Everybody was a bit confused, everybody obviously thought of 9/11."
Thousands of commuters evacuated the train terminal, some at a run, after workers yelled for people to get out of the building. A small school bus was abandoned just feet from the spot where the jet of steam spewed from the ground.
Large crowds of homeward-bound commuters milled in the streets around Grand Central Terminal, nervously sharing information. Inside the station, food vendors hurried to store their carts and yelled to commuters that they had been ordered to evacuate. Commuters pouring into the station began turning around to exit to the street.
For some time after the explosion, no uniformed police or emergency personnel could be seen at the northern Madison Avenue entrance to Grand Central, a major entry point to the station, according to NBC News' Mark Lukasiewicz. Commuters there relied on cell phones, passersby and Blackberries to decide whether it was safe to enter the station.
Debbie Tontodonato, 40, a manager for Clear Channel Outdoor, said she thought the rumble from the explosion was thunder.
"I looked out the window and I saw these huge chunks that I thought were hail," she said. "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."
Streets, subways closed
Streets were closed in several blocks in all directions. Subway service in the area was suspended.
The steam cleared around 8 p.m., exposing a crater several feet wide in the street. A red tow truck lay at the bottom of the hole.
Con Edison spokesman Chris Olert said workers were still trying to determine what caused the blast.
There were also concerns about what was spewed into the air. Some of the pipes carrying steam through the city are wrapped in asbestos. Olert said asbestos testing was under way.
Police were wearing gas masks on the street.
Millions of pounds of 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. In 1989, a gigantic steam explosion ripped through a street, killing three people and sending mud and debris several stories into the air.
That explosion was caused by a condition known as "water hammer," the result of condensation of water inside a steam pipe.