July 18 (Bloomberg) -- A steam pipe exploded near Manhattan's Grand Central Terminal during the evening rush hour, sending plumes of steam and debris into the air, killing one person and injuring at least 20.

The blast occurred shortly before 6 p.m. a block from Grand Central, through which more than 700,000 commuters pass every day. There was one death, and other people injured at the scene were being treated at Manhattan's Bellevue Hospital Center and New York Presbyterian Hospital-Weill Cornell Medical Center.

``There is no reason to believe whatsoever that this is anything other than a failure of our infrastructure,'' said Mayor Michael Bloomberg at a press conference at the scene.

Bloomberg said the explosion may have been caused by cold water that got into a 24-inch steam pipe that was installed in 1924. The mayor said it wasn't clear whether any asbestos was released during the explosion, which occurred at the intersection of Lexington Avenue and 41st Street. City officials were taking air samples at the site and police set up a no- traffic ``frozen zone'' from 40th to 43rd Streets between Vanderbilt and Third avenues, Bloomberg said.

Joe Petta, a spokesman for utility owner Consolidated Edison Inc., said there were no power failures associated with the blast and the cause was unknown.

``We are assessing possible collateral damage,'' Petta said. ``This is an all-hands event. Anybody who was on their way home turned around. Anyone who's here stayed.''

Subway Disruptions

Service on parts of the 4, 5 and 6 subway lines that run along Lexington Avenue was shut down or diverted to other lines while the shuttle to Times Square wasn't operating and the 7 line wasn't stopping at Grand Central, said Elliot Sander, the executive director of the Metropolitan Transportation Authority, which oversees city subways and buses.

Metro North commuter rail service is running normally, according to the MTA's Web site.

The Office of Emergency Management can't confirm whether the debris in the area is hazardous, said spokeswoman Lisa Schulman.

``If you don't need to be in the area right now you shouldn't be,'' she said.

Bloomberg said people exposed to debris should wash with soap and water and any clothing worn at the scene should be placed in plastic bags. He asked that no one enter the blast area while the clean-up and air tests continue.

`Rush of People'

After today's blast, about 200 members of the city fire department from 40 units rushed to the site, according to fire department spokesman Tony Sclafani. Some onlookers said the scene was reminiscent of the Sept. 11 attack on the World Trade Center.

Cassie Sanchez, a 32-year old administrative aide at Sentinel Capital Partners who said she was in the World Trade Center when it was attacked, was sitting in an open air bar beside Grand Central when she heard a tremendous roar.

``We saw a rush of people and we're hysterical, we started to run,'' Sanchez said. ``It was like what we saw on Sept. 11.''

Joe Barton, a security officer at 370 Lexington Ave. near where the explosion occurred, said bricks and debris were ``just flying all over the place.''

Brick, glass, asphalt and dirt covered cars and bicycles and littered the street for a block past the blast site. Injured people spackled in brown wet dust were treated for minor injuries at the scene, and abandoned high-heeled shoes and flip flops were strewn across the sidewalk.

Largest Steam System

Manhattan is home to the largest district steam system in the world, according to the Web site of the city's Economic Development Corp. While most of the city's buildings have on- site boilers to provide heat during the winter, the Con Edison Steam Business Unit heats 1,800 buildings, serving more than 100,000 commercial and residential customers through a series of underground pipes running from the Bowery in lower Manhattan to 96th Street.

Con Edison's steam network links many end-users to central power plants through a network of pipes carrying either steam or heated/cooled water under high pressure. The New York Steam Co. began providing such service in lower Manhattan in 1882.

In 2000, a steam pipe explosion near New York University's Bobst Library on Washington Square blew a 15-foot crater into the street on Washington Square South, and spewed debris and traces of asbestos into the air.

In 1989, a steam pipe exploded in Manhattan's Grammercy Park, killing three people and sending mud and debris several stories into the air.

The mayor is the founder and majority owner of Bloomberg News parent Bloomberg LP.

To contact the reporters on this story: David M. Levitt in New York at dlevitt@bloomberg.net; Henry Goldman in New York at hgoldman@bloomberg.net.

Last Updated: July 18, 2007 21:47 EDT