NYPD arson and explosion investigators found the gas plumbing largely intact Thursday after finally reaching the cellars of two East Village buildings destroyed in a March 26 explosion, but officials would not say whether there were any signs of tampering.

After the blast, which killed two and injured 22, Mayor Bill de Blasio said evidence showed a natural gas line had been improperly accessed to provide service to the building at 121 Second Ave. Two other buildings were also leveled in the explosion.

An inspection Thursday of the debris and plumbing in the cellar of 121 Second Ave., where contractors were adding a new plumbing and gas system before the blast, found it "surprisingly intact," a law enforcement source said.

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The gas lines inside 119 Second Ave. were in similar condition, said Chief of Detectives Robert Boyce. He wouldn't elaborate on what else investigators discovered.

Before the blast, Con Edison inspectors checked the plumbing work inside the first floor of a Japanese restaurant at 121 Second Ave. Gas was approved for the restaurant through a 11 /4-inch pipe.

The plumbing work failed two inspections, including one less than an hour before the blast, Con Edison officials said.

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A 3-inch pipe providing gas to other tenants was locked after a failed inspection, Con Edison said. Among the problems were improper placement of the meter, officials said.

Investigators are checking statements that tenants received gas service from an illegally tapped line in the restaurant and were told before the explosion that it would be temporarily interrupted and not to tell Con Edison inspectors they had gas, officials have said.

A lawyer for building owner Maria Hrynenko said that given the volume of gas that accumulated, it was inconceivable inspectors didn't notice. Hrynenko, of Rockland County, inherited the building from her late husband, Michael, said attorney Thomas M. Curtis.

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"There wouldn't have been enough gas in the premises unless it was there when Con Ed was there," Curtis said. "In my book, either Con Ed didn't have the new [3-inch] pipe shut off completely, or the old [smaller] pipe was leaking when they were there."

A Con Edison spokesman didn't return a call for comment. Mark McDonald, a gas consultant at Nat Gas Consulting not involved in the case, thought it unlikely Con Edison would ignore signs of trouble.

"I find it hard to believe Con Ed would walk away after viewing a hazardous situation or something done illegal," said McDonald. "There is no incentive not to do what it is supposed to do."