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EAST HARLEM (PIX11) — Four people were killed and at least 63 people were injured after a massive gas explosion leveled two five-story buildings in East Harlem Wednesday morning in a blast that literally jolted a chunk of the city.

One of the victims has been identified as 44-year-old Hunter College public safety officer Griselde Camacho.  She started working with the school in 2008.  Another has been identified as 67-year-old Carmen Tanco.

Nine people were still missing Wednesday night, according to Fire Marshals and the NYPD, and rescuers have yet to bring in heavy equipment required to enter the heart of the devastation.

As the search for victims continued amid rain and dropping temperatures, rescuers’ efforts were hampered by a sinkhole in front of the buildings, according to city officials.  The sinkhole was caused by a water main possibly broken in the explosion, and is preventing heavy equipment from reaching the site.

The aftermath of the blast was captured in residents’ photos posted online.

The explosion happened on 116th Street and Park Avenue just after 9:30 a.m., 15 minutes after Con Edison has received a call about the smell of gas at 1652 Park Ave. Smoke continued to pour out of the site of the explosion, where as many as 255 firefighters were knocking down the fire.

Neighbors had been complaining of the smell of gas for days before the explosion, but Con Edison said it had received no reports of a problem there until this morning, minutes before the blast.

The National Transportation Safety Board, which oversees gas-pipe infrastructure,  is investigating but hasn’t had a chance to explore the site in any depth yet.

The agency said old cast-iron pipes like the one feeding the destroyed buildings are a source of concern, and have played roles in explosions in Birmingham, Ala. and Allentown, Pa.

It was too early to know what the possible cause may be of the East Harlem  natural gas explosion.

Firefighters work to knock down the blaze.

“There was no warning in advance,” Mayor Bill de Blasio said during a news conference.  “It’s a tragedy of the worst kind because there was no indication.”

The blast left a scene of utter devastation, with firefighters mounting the piles of rubble as they carefully used buckets to cart out debris.

Glass, brick and other debris were flung far and wide, including on Metro-North tracks across from the buildings that were destroyed, which housed a church and a piano repair shop, and apartments above. The blast reduced the air quality for miles around the blast scene, with a chunk of the city covered in acrid smoke.

Many likened the blast to an earthquake, and indeed, the blast registered just under a .5 on seismograms geologists use to measure temblors.

Some 22 were treated — including three children — at Mount Sinai Medical Center, and most injuries were minor. Two of the children have already been treated and released.  Only one injury — a head wound — was described as serious.  Forty-one other people were treated at Harlem Hospital, Metropolitan Hospital and New York Presbyterian-Weill Cornell Medical Center.

Two FBI agents and an off-duty NYPD officer also were hurt in the blast’s aftermath.

Crews work to clear debris from the two buildings that collapsed.

The blast was felt miles away, with one PIX11 viewer feeling the shake reporting she felt the blast on 174th Street in the Bronx.

Spanish Christian Church at 1644 Park Ave. and Absolute Piano Repair at 1646 Park Ave. were on the first floors of the buildings.

The buildings before the explosion. (Photo: Twitter @Marjan_Lion)

About 75 Con Edison personnel were on the site Wednesday afternoon, all electric and gas service was shut down along the west side of Park Avenue between East 116th and East 117th, as well as on the north side of East 116th near Park Avenue.

Witnesses have told PIX11 that there are at least 39 units in one of the buildings.

Two good Samaritans, David Cersario and Alex Camilo, who were working across the street helped rescue a child from the rubble.

“[The child] had a controller for a PlayStation in his hand,” David said of the child, who is about seven- or eight-years-old and was lying in the debris.

(Photo: Twitter FDNY)

The two men carried the child to safety and tried to rescue more people, but were told that the scene was too dangerous by cops and firefighters.

(Photo: Kirstin Cole/WPIX)

“I actually thought the train had either collided with another train or fell off. That’s how loud the boom was. I live a block away And the sound of that I actually thought it was an earthquake. The way it sounded for a minute,” said neighborhood resident Brandon Whitaker.

Justine Rodriguez, who lives right next to the explosion site, said, the explosion shook her from sleep.

“Well I was asleep. My bed was right next to the windows. As soon as the windows came crashing and it’s all over my bed and floors. It cut me up in the back of my leg. I’m just thankful that no one else was home,” Rodriguez said.

Rodriguez had also contacted Con Edison before the explosion.

“My mom said she had smelled gas before leaving to work with my sister. They smelled gas since very early in the morning. I heard they contacted Con Ed before the explosion,” she said.

A woman who identified herself as Ayesha panicked after she was trapped in the apartment.

“I was trapped in the apartment. I had to think fast and get a knife to get the locks opened. That didn’t work, so I started hitting the door  and calling for help but my neighbor kicked the door open. Thank God I had ran down the stairs and as I got out of the building — there were bodies laying around. I didn’t know what was going on. This was beyond a trail derailment or something. I was just scared out of my mind. ”

This is a developing story; stay with PIX11 for updates.