NEW YORK (CNN) -- The air was declared clean, but the carcinogen asbestos was found in dust and debris hurled into midtown Manhattan by a steam pipe explosion the day before, New York City announced Thursday.
A steam pipe burst in midtown Manhattan during rush hour Wednesday.
The city's Department of Emergency Management will continue to test the debris after finding asbestos in six of 10 samples, according to a statement from the city's Office of Emergency Management.
"People who may (have come) into contact with the steam or debris should take a shower and place their clothes in plastic bags for cleaning or disposal," the statement said.
Asbestos is a fibrous mineral used to insulate pipes. Longterm exposure can cause allergies, skin problems and cancer.
The 6 p.m. blast, which sent sent plumes of smoke and ash into the air around Grand Central Terminal, killed a woman and injured at least 44, according to authorities and local hospitals. Watch an I-Reporter's video of "volcano" in street »
Lois Baumerich, of Hawthorne, New Jersey, died of cardiac arrest, New York City Mayor Michael Bloomberg said.
Three firefighters and a police officer were treated on the scene for minor injuries, according to a New York Fire Department spokesman.
Bellevue Hospital Center received 14 patients, including Baumerich, hospital Administrator Larry Dugan said. New York Presbyterian Hospital said it received 27 injured people, 25 of whom were treated and released. As of Thursday, one person was listed in critical condition and another in serious.
The area encompassed by 40th and 43rd streets and Vanderbilt and Third avenues was "frozen" because of the asbestos threat. Map of blast site »
Those in that zone are allowed to stay in the area, but should use caution. No one will be allowed to enter the zone, the Office of Emergency Management said.
"People inside buildings in the frozen zone should keep windows closed and switch air conditioners to recirculate the air inside instead of drawing in air from outside," the office said.
Also, parts of Lexington Avenue, Third Avenue, Park Avenue, 42nd Street and Vanderbilt Avenue will be closed to traffic.
Subway lines near the explosion were initially rerouted to bypass Grand Central Terminal, but the Metropolitan Transportation Authority said Thursday the subway infrastructure was not damaged.
Bloomberg told reporters the pipe that exploded was installed in 1924.
"There was cold water getting into the pipe, and cold water apparently causes these to explode," the mayor said. "It might have been bursts of cold water from the rain or because of another water main break."
Hundreds of people frantically fled the scene as police, fire and utility officials converged on the area around the blast, which left a crater 25 feet wide and 15 feet deep, according to utility provider Con Edison. More than 170 firefighters were dispatched to the site, the fire department said. Blast leaves massive crater »
"The ground was literally shaking under your feet," New York police Deputy Commission Paul Browne said.
Video from the scene showed steam and mud erupting from underground. A small school bus had its windows and one of its doors blown out.
One witness, former CNN reporter Adaora Udoji, described the scene as "pandemonium." Within about 20 minutes, she said, authorities had the entire area locked down.
"It felt like an earthquake. We saw hundreds and hundreds of people running down Third Avenue," she said. "They were screaming, they were crying."
The New York Times reported that the rush-hour blast sent up a geyser of steam, mud and rust-colored gunk, and displaced chunks of pavement in one of the busiest parts of the city.
Pedestrians scrambled to flee the blast -- some running out of their shoes -- as those working in the skyscrapers pelted with debris looked down in horror, the newspaper reported, comparing the aftermath of the blast to a hailstorm.
Some witnesses said the jet of steam roared like Niagara Falls, The New York Times reported.
Carol Bergendale, who witnessed the blast, told WABC that commuters in the area began driving in the wrong direction to get away.
Despite initial fears, Browne said the blast had nothing to do with terrorism, and the FBI said there was nothing suspicious about the blast.
In August of 1989, three people died related to a steam pipe explosion in Gramercy Park. E-mail to a friend
CNN's Amy Sahba and Katy Byron contributed to this report.
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