At least 19 people were injured Thursday, three of them critically, in a suspected gas explosion and a subsequent seven-alarm fire originating at 121 Second Ave. in New York City’s East Village neighborhood. Two of the critically injured suffered burns to their airways while the other fell unconscious following the explosion, according to Fire Department of New York Commissioner Daniel Nigro, who added that the “majority of those injured were injured in the initial explosion.”

Two adjoining buildings, 119 and 125 Second Ave., have been directly affected by the fire, while two others, 121 and 123 Second Ave., collapsed. The FDNY contained the fire to those four buildings as of 6 p.m. EDT.

In a televised press conference, Mayor Bill de Blasio said independent contractors were working on the gas systems at 121 Second Ave. just prior to the explosion, although a reason for the explosion has not been verified. Con Edison, the utility company that supplies most of the city’s buildings with gas, had inspected a new meter system at the building at around 2 p.m. EDT Thursday. The work was ultimately not approved and Con Edison provided instructions for fixing those issues. It was unclear if that work is related to the explosion.

“We have the Department of Environmental Protection hazmat operation responding to check for the environmental impact and the health impact,” said de Blasio.

The city has set up a Red Cross assistance center at Public School 63 at 121 East Third St. Those affected by the fire can go there to receive care and other assistance. Those concerned about possible health issues related to the explosion, subsequent fire and smoke can visit East Village Explosion FDNY responders walk towards the fire, which has consumed four buildings, collapsing two of them in New York's East Village neighborhood Photo: Reuters/Mike Segar

Businesses at the ground floors of the four buildings include two sushi restaurants, a deli and Pommes Frites, a restaurant that the New York Daily News said has the “best French fries in New York City.” Each of the six-to-seven-story buildings were built around 1900, according to Property Shark. Photos and videos of the fire are available here.

A seven-alarm is declared when a blaze requires around 250 firefighters and 45 pieces of equipment, including engine trucks, ladder trucks and specialty trucks, along with EMT responders, according to the FDNY. More photos from the scene follow below:

East Village Explosion Mayor Bill de Blasio called the fire a "tragedy." Photo: Paul McDougall/IBTimes manhattan_fire_720 The explosion and fire engulfed 119, 121, 123 and 125 2nd ave in Manhattan's East Village neighborhood. Photo: Paul McDougall/IBTimes