Workers have said they were told to repair a gas pipe authorities suspect sparked the East Village blast on March 26 that leveled three buildings, killed two people and injured 22 others, according to a law enforcement source familiar with the investigation.

It was not clear who the workers said told them to work on the the gas pipe in the basement of the building at 121 Second Ave., said the official, who asked not to be identified.

He said "it is likely that this case turns into a homicide investigation" but not until the Manhattan district attorney's office determines who caused the blast and decides whether to file criminal charges.

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Investigators suspect a leak from an illegal tap into the pipe led to the explosion and fire. The investigation could extend well into 2016, the official said.

A spokeswoman for Manhattan District Attorney Cyrus Vance Jr. declined to comment. The office took nearly two years to bring charges in a fatal 2008 crane collapse in Manhattan. According to officials, 121 Second Ave. was authorized to have gas service through a 1 1/4-inch line only for a restaurant on the first floor.

Con Edison, whose inspectors visited the site an hour before the blast, for months wouldn't allow service through a 3-inch pipe for other tenants because of, among other things, problems with the placement of the meter.

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Investigators were told someone alerted tenants that gas service would be temporarily shut off on March 26 and to not tell Con Edison inspectors there that they had it, the official said.

The general contractor on the building was Dilber Kukic and the plumbing contractor was Andrew Trombettas, according to city records and officials. Trombettas, a licensed plumber, is affiliated with SK Piping & Heating Corp. and Beta Plumbing & Heating Corp., according to corporation records. One crucial question is whether illegal tapping of the gas line was done incorrectly or in a negligent manner.

"They can't indict here by saying gas is dangerous," said a former prosecutor who didn't want to be identified, explaining that the siphoning of gas alone may not lead to manslaughter charges.

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Trombettas, whose offices are in Long Island City, didn't return calls. Mark Bederow, an attorney for Kukic, said "people should not draw conclusions of causations of the tragedy until the investigation is completed."