New York City Fire Department firefighters battle fire at the site of a residential apartment building collapse and fire in New York City's East Village neighborhood, March 26, 2015.[Photo/Agencies]

Adil Choudhury, who lives a block away, ran outside when he heard "a huge boom."

"Already there was smoke everywhere." when he saw the building, he said. "The flames were coming out from the roof. The fire was coming out of every window."

Items from a ground-floor sushi restaurant were blown into a street, and the explosion was so forceful that it blew the door off a cafe across the avenue. Rubble, glass and debris littered sidewalks.

Con Ed crews planned to start investigating after firefighters got the blaze under control. The state Department of Public Service was monitoring Con Ed's response, Gov. Andrew Cuomo said.

Area resident Paul Schoengold said he was walking about two blocks away when he heard an ``incredibly loud'' roar.

"Then the fire started. I could see the flames on the roof, and they kept getting higher," shooting perhaps 50 feet into the air, he said.

Other witnesses said a woman scrambled down her fire escape in the moments after the explosion. She stopped on the second floor, afraid to go further, and passers-by climbed up to help get her down.

In the aftermath, one person was lying on the ground, being attended to by two to three passers-by who were holding his head still, Seto said. A woman was sitting on the curb with blood coming down her face, and another woman walked past him with blood on her face, he said.