ABC7 reports that the Manhattan District Attorney’s office is now “fully engaged” in the investigation of the East Village blast. “This is going to be a slow, methodical investigation,” a law enforcement source told the New York Post. “We will be talking to everybody — witnesses, the contractor, the plumbers and landlord, gas experts — to see if there was criminal negligence.”

Law enforcement has been interviewing utility workers, business owners, and witness who were present at the site on Thursday afternoon in an effort to piece together what caused the blast, which leveled three buildings and ignited a fire that took three days to fully extinguish on Second Avenue near 7th Street. It is now believed to have been caused by an unauthorized gas line, reports the New York Times:

Their working theory is that one or more gas lines were surreptitiously tapped over several months; then the siphoning apparatus was dismantled or hidden on Thursday before Consolidated Edison conducted an inspection. As soon as the utility inspectors left, an attempt to resume the diversion of gas went awry, setting off the explosion, according to two law enforcement sources with knowledge of this working theory.

Two people died and 22 people were injured from the explosion, four critically. The fire displaced dozens of families. You can help by donating to the funeral of one of victims, Nicholas Figueroa ,here. For other resources on how to help, check out EV Grieve’s list here.

(Photo: FDNY)