Authorities today responded to a seven-alarm fire after a building explosion and collapse in New York City’s East Village.

MyFoxNY.com reported that four residential buildings were affected by the fire, and at least a dozen people were injured – three critically.

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Mayor Bill de Blasio and other city officials said the explosion may have been gas-related. Workers were installing a new meter and other gas equipment. Con Edison inspectors examined the equipment and failed it.

About an hour later, the explosion occurred. De Blasio said there are no indications that anyone called either 911 or 311 to report a smell of gas. The city and Con Edison are investigating.

Officials said that a shelter has been set up at P.S. 63 at 121 East 3rd Street. The American Red Cross is there to help displaced residents.

See photos from the massive fire below.