A gas explosion at an apartment in New York City has left nine people injured, including two children who are in critical condition, police and fire officials said.

Six out of the nine injured are children, police sources said. The youngest is a 5-year-old.

In addition to the nine civilians, one firefighter suffered non-life-threatening injuries.

The blast occurred on the second floor of an apartment in the Bronx, blowing the front door off the home and into a tree, sources said. Most walls were blow out, too, sources said.

“I burst open my door next door and I saw my grandfather was OK,” building resident Adriel Sambolin told New York ABC station WABC. “We hopped out the window in the back because we had no more window.”

“I opened the door and packed my bag, threw my phone, my wallet and then jumped out the back and he jumped out with me and I jumped that gate to see if everyone was OK,” he added.

“We received a call for an explosion. Units responded on scene in three minutes and found what appeared to be a gas explosion with heavy damage to the front of the buildings,” FDNY Deputy Assistant Chief John Sarrocco said from a press conference at the scene. “There were windows and doors blown out and several victims within the structure. Units entered the structure, rescued approximately eight patients, two of which were in critical condition.”

Photos from the scene showed sliding glass doors completely blown out and debris blown over the decks and onto the cars in the driveway below.