NEW YORK (CBSNewYork) -- A high-pressure steam pipe exploded Thursday in the Flatiron District, sending large plumes of steam pouring into the air.
Speaking at a news conference, Mayor Bill de Blasio said test results have confirmed the presence of asbestos.
"There was asbestos is the steam line casing," he said. "That's obviously a real concern for us."
Officials said the potentially cancer-causing substance was found in the aging pipe but not in the air, which is safe to breathe.
The 20-inch pipe, which Fire Commissioner Daniel Nigro said was installed in 1932, burst around 6:40 a.m. on Fifth Avenue between 22nd and 21st streets.
More than 100 firefighters responded to the scene along with the NYPD and crews from Con Edison. A large hole could be seen in the street where the explosion occurred as thick white steam came billowing up from the ground.
"We have also tested the air since the time of the incident. The air cleared fairly quickly after the incident so the air in this area now is safe. There is no meaningful presence of asbestos in the air at this point," de Blasio said. "Our concern is the debris that was thrown off by the rupture. Some of that is still visible on the street and the building facades."
The mayor said officials are worried about whether any debris entered into buildings or air conditioning systems.
"There is going to be a thorough assessment to make sure that all the buildings are clean and safe," de Blasio said.
As a precaution, Con Ed is urging anyone in the area at the time of the blast who may have been covered in any debris to bag their clothes and take a shower.
De Blasio said if anything could have gotten on a person's clothing, it needs to be removed, bagged and turned in to Con Ed at 22nd and Broadway, which will provide reimbursement.
"Brief exposure is not a problem through the air but if this material is in a building, on clothing, that is a real concern," he said.
Forty-nine buildings were evacuated and de Blasio said they may remain closed off for at least a couple of days.
"For people who live and work in these buildings, we are going to their best to help them get back in as soon as possible," he said. "If people have particular urgent needs such as medicines they left in their apartment or a pet that was left in a apartment, FDNY and NYPD will help address those issues and can send properly trained, properly equipped officers into those apartments."
Nigro said two decontamination stations have also been set up at 22nd Street and at 19th Street.
"Anyone who feels like they were affected by this and possibly contaminated can report there for evaluation," he said.
Eight people suffered minor injuries, including five civilians, from the debris, Nigro said. Five hundred people were displaced from 249 residential units.
Officials said it could take days to clean up the area and people should continue to expect traffic delays, road closures and emergency personnel at the scene.
In a statement, Gov. Andrew Cuomo said he is directing the Department of Public Service "to conduct a full investigation into the cause of this explosion and determine whether any utility activities contributed to it."
"In conjunction with that investigation, the Departments of Environmental Conservation and Labor are standing by to assist in asbestos testing, assessment and with the disposal of contaminated material," he said.
Fifth Avenue is closed to traffic from 25th Street to 19th Street, Broadway is closed from 23rd Street to 17th Street, and 19th Street to 22nd Street are closed between Fifth and Sixth Avenues.
M14A, M14D and M23-SBS buses are running with delays in both directions. Southbound M1, M2, M3 and M55 buses are making stops on 7 Av from 31 St to 15 St, and northbound M1, M2, M3 and M55 buses are delayed.
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