Asbestos has been found at the site where an underground steam pipe exploded early Thursday morning near the Flatiron building in midtown Manhattan.

Mayor Bill de Blasio says the cancer-causing substance has been found around the aging steam pipe that exploded in Manhattan, according to the Associated Press, but that the air is safe. Reuters reports the asbestos had encased the 86-year-old pipe.

The mayor says streets will likely be closed for a few days in the area of the blast early Thursday under 21st Street at Fifth Avenue, the AP reports. The explosion caused the evacuation of 49 buildings but only minor injuries to five people.

Gov. Andrew Cuomo says he has directed the Department of Public Service to conduct a full investigation into the cause of the steam pipe explosion in Manhattan, according to the AP.

Officials earlier warned people who may have gotten material on them to bag their clothes and shower immediately because of the possibility of asbestos. Con Edison said on its Twitter account that it's collecting, for testing, clothes worn by people who during the blast were within 500 feet east or west of Fifth Avenue on 20th and 21st streets or were within 100 feet north and south of it on Fifth Avenue.

"We're at 19th St & Broadway and at 22nd St & Broadway until 9 p.m. to accept the clothing. Claim forms are available for people to submit to receive compensation for their clothes. We'll also be in the Clinton School, 10 East 15th St., until 10 p.m. to provide claim forms," Con Edison tweeted.

Responders are wearing face masks in the so-called hot zone, and their vehicles have been hosed off.

Fifth Avenue remained closed to traffic into early Thursday evening. Up to three helicopters hovered over the spot just before 6 p.m.

Cleanup could take days if asbestos is found at the scene, Office of Emergency Management Commissioner Joseph Esposito said before the contaminant was confirmed.

The underground steam pipe network in the area has been shut down. A Con Edison executive told the AP that the effects of the shutdown will include loss of air conditioning and hot water to affected buildings. Con Edison’s website says its steam service system is the largest in the U.S., serving 3 million people from the tip of southern Manhattan to 96 St.

Reuters reports that according to New York City Fire Commissioner Daniel Nigro, the force of the blast may have damaged other subterranean lines in the vicinity that carry water, gas and electricity, and that all have been shut down until repair work is done.

Jennifer Brown, of the Flatiron 23rd Street Partnership, told the AP that a wide variety of businesses, from restaurants to retailers, are closed along Broadway and Fifth Avenue from 19th to 23rd streets. The blast also affected larger buildings with commercial office space.

The 23rd Street Partnership says it has public safety officers, a clean team and other forms of assistance at the ready.