EAST HARLEM — Federal investigators outlined their strategy Thursday for getting to the bottom of the explosion that leveled two East Harlem Building explosions and so far killed seven people.
"We are operating under the assumption at this point that this was a natural gas leak," National Transportation Safety Board member Robert Sumwalt said during an afternoon press conference.
The NTSB, which monitors rail, aviation and highway accidents, also investigates natural gas pipeline failures.
The probe has not yet begun because pockets of fire are still burning where 1644 and 1646 Park Ave. crumbled, a fire department spokesman said.
"This is an active search and rescue operation with first responders carefully removing debris. Because of the nature of the scene we are not able to get up close and personal to look at the pipes," Sumwalt said.
Once it gets clearance the agency will run a pressure test on the main pipe running under Park Avenue and feeder pipes leading into the two buildings, he said.
The NTSB also requested information from Con Edison on the age, diameter and thickness of pipes.
The agency has not eliminated the possibility that the leak came from an outside source like a stove.
The NTSB is also requesting all 311, 911 and 811 — which is used by utility companies and contractors before digging up a road or sidewalk — records from the city.
There was a call at 9:13 a.m. Wednesday from a resident reporting a gas smell. Crews were dispatched at 9:15 a.m. and the explosion happened at 9:31 a.m., before the trucks arrived.
"We've gone back and looked at any gas calls on that block, going back three years, and we found two calls prior to yesterday," said John McAvoy, CEO of Con Edison at a separate press conference Thursday afternoon. "One was May 17, 2013 and one was January 26, 2011. Both were on customer equipment internal to the building, and both were repaired at those dates. Other than those two, going back three years for the entire block, no other — no reports of any gas leaks from the area."
The NTSB was also still not sure about what factor a water main break may have played in the explosion.
"We don't know if [the water main break] was a result of the explosion or if it led to the explosion," Sumwalt said.
FDNY investigators have been loading the building debris onto trucks with a backhoe and shipping it to Randall's Island to sift through.