Surveillance videos that captured Wednesday’s deadly East Harlem blast have been found by police, evidence that a forensic expert said could provide crucial information on how the explosion that killed eight people occurred.

NYPD Commissioner Bill Bratton revealed Thursday that the recordings were taken by neighborhood security cameras and secured by police shortly after the explosion leveled two buildings on Park Avenue at 116th Street.

Bratton didn’t go into details about what the videos captured, but the recordings are part of a laborious investigation involving the National Transportation Safety Board, the FDNY, NYPD, state utility regulators, the fire marshal’s office and Con Edison.

Robert Malanga, an engineer who specializes in fires and explosions, said the footage could indicate if the explosion began in the upper or lower stories of the buildings, a clue to how long gas was leaking.

“If you had a slow developing leak, it would tend to migrate to the upper part of the building and reach explosive limits,” Malanga said. “A rapidly developing leak would tend to center down closer to the ground.”

News of the video came on a day federal investigators waited for a smoldering fire to clear from a massive pile of debris before testing gas-distribution lines and hunting for other clues to the blast that killed eight  people and injured scores.

About 150 firefighters continued work at the Park Avenue scene, where rescuers found an eighth body in the rubble Thursday evening.

Overnight, the site became more precarious after a back wall burned, and during the day, strong winds whipped embers in the debris, stoking hot spots.

The smoldering fire sent out plumes of gray smoke, which billowed into an air-quality nightmare. About 90 nearby homes and three businesses in area buildings were evacuated. City officials warned people nearby to stay indoors and close their windows.

Despite the wind and chill, rescuers with grapples went through piles of rubble to look for victims at the  scene.

“You’ve got basically two five-story buildings that have been reduced to essentially a three-story pile of bricks and twisted metal,” Robert Sumwalt, board member of the National Transportation Safety Board, told  reporters near the scene.

“I’ve seen an occasional flare-up of fire, and the smell of smoke is omnipresent. All of this underscores that this is an active search-and-recovery operation.”

City officials Thursday night would not say how many people remained unaccounted for. They appeared to be backing away from Wednesday night’s estimate that as many as nine people were missing, a time when only three bodies had been discovered.

Once conditions become safer, investigators will run a pressure test on the gas-distribution line that runs along Park Avenue, Sumwalt said.

The line did not show any “obvious to the eye” damage from what officials could see after a sinkhole opened in front of the buildings and after parts of the street were excavated, he said. If no leaks are found, service lines from the distribution pipe to the buildings will be tested, he said.

“We are operating under the assumption at this point that it was a natural gas leak,” Sumwalt said.

Investigators want to pinpoint whether the infrastructure was to blame or if the leak stemmed from something like a stove.

They also want to know if a water-main break, which caused the sinkhole, led to the leak or if it was the other way around.

Sumwalt said the NTSB had set up four teams of investigators on key issues: emergency response, operations, public awareness and “integrity management,” covering inspections, reviews and other processes by parties involved, including city agencies and Con Edison.

The blast was reported soon after 9:30 a.m. Wednesday, after a caller at 9:13 a.m. told Con Edison that he smelled gas fumes that morning and the night before.
If more people had reported the gas leak in East Harlem “there’s a very high likelihood” the fatal explosion could have been prevented, Con Edison’s chief executive said Thursday.

John McAvoy said  gas had probably been leaking overnight, explaining the caller’s report had been classified as “low” priority instead of an urgent case, which would have alerted the fire department while utility crews responded.

Con Edison dispatched workers at 9:15, but they arrived just after the explosion.
“Had calls come in earlier than that, the likelihood of us being able to address it is good because we address calls like this all the time,” McAvoy said Thursday at a news conference in front of City Hall.

Sumwalt of the NTSB said he’d like investigators to speak with residents who reported they’d smelled natural gas before the explosion.

Investigators have begun looking at the history of reports about gas fumes, third-party digging in the area and the conditions of the pipe infrastructure.

McAvoy said Con Ed had searched its records going back three years and found only two calls about gas problems on the block where the explosion took place, and both of those, in 2011 and 2013, were problems with the customer’s equipment.

Fire Commissioner Sal Cassano said his agency checked records for the past 30 days and found no reports of gas leaks in any building in the immediate area.

“This has been a very painful episode for the people of Harlem,” Mayor Bill de Blasio said at a news conference Thursday. “There are still a lot of unknowns here.”
The mayor noted the “exemplary job” done by firefighters working the scene.

“Everyone involved in the rescue effort has given their all,” de Blasio said, noting they have stuck with it in difficult circumstances — the wind and the cold.

He said the operation will “continue for days”: “We are continuing the rescue operation, hoping to find others still alive.”

Asked to update the number of missing, de Blasio said, “We are being very careful. There are still questions about the whereabouts of individuals.”

Officials at hospitals said they still had eight patients Thursday, including a woman pulled from the rubble with serious head injuries. Four hospitals had reported treating a total of 67 blast victims.

Scores of people who lost their homes gathered Thursday at the Salvation Army Community Center on 125th Street to get help.

The blast sent chunks of 1644 and 1646 Park Ave. flying into nearby buildings, raining down on passersby, flattening cars and hurtling into windows of nearby buildings.

Debris also landed on the nearby train overpass, shutting down Metro-North rail service into Grand Central Terminal for much of the day.

Officials said 40 people had been taken to hospitals, including two with life-threatening injuries, the mayor’s office and police said. Four hospitals treating victims reported a higher total because many were walk-ins.

The intense blast was felt blocks away, and several witnesses said they thought it was an earthquake.

One victim was identified by Hunter College in Manhattan as Griselde Camacho, 45, a sergeant in the college’s public safety office since 2008. Officials from Bethel Gospel Assembly, a 97-year-old church four blocks from the blast site, late Wednesday identified two of the deceased as members Carmen Tanco, 67, and Camacho.

The two women lived in apartments at 1646 Park Ave., said Ruth-Ann Wynter, Bethel’s director of ministry relations.

An NYPD spokeswoman, Det. Annette Markowski, confirmed those identities Thursday morning as well as that of another victim, Rosaura Hernandez-Barrios, 22, also a building resident.