State investigators have concluded a 20-month probe into the East Harlem gas explosion of March 2014—which killed eight people and left more than 20 injured—and Con Edison may now face fines or legal action for its alleged involvement in the blast.

The deadly explosion took place shortly after 9:30 a.m. last March 12th, at 1646 and 1644 Park Avenue on the corner of East 116th Street. Neighbors had reportedly failed to report a strong gas odor for days prior.

The Public Service Commission announced its findings in a meeting on Thursday afternoon. According to the PSC, the explosion was caused by soil erosion under the street that put pressure on a gas line that had been poorly and improperly fused. The pressure caused a leak that went on for days leading up to the explosion.

A separate investigation conducted by the National Transportation Safety Board faulted Con Edison over the summer, placing blame on city government as well. According to the NTSB, the poorly-welded joint wasn't helped by a breached sewer main on the block—one that the city had allegedly ignored for years. Con Edison filed suit against the city in June, claiming that the NYC Department of Transportation knew about "depressions and cave-ins in the roadway" at Park Avenue between East 116th and East 177th streets.

The PSC report also accuses Con Ed of not adequately training or certifying its workers in pipe-fusing, and failing to install the correct valves to prevent gas leaks. According to the PSC, the contractor who fused the fated joint had let his certification expire the month previous.

"We maintain that a cracked fitting, damaged by undermined street infrastructure from a pre-existing sewer breach, was the source of the leak that led to the East Harlem gas explosion," said Con Ed in a statement to Capital. The company has a month to respond to the findings in more detail.

The city has challenged Con Ed's account. In June, the Mayor's office stated, "The rupture in the City’s water main occurred as a result of the explosion, not due to the damaged sewer.... Put simply, the full investigation reveals that a properly fused fusion joint would not have failed."

Any fines or civil penalties as a result of the PSC report are pending.