Police officials confirmed Thursday that a leak in an illegal gas connection caused Tuesday's deadly house explosion in the Bronx, and that the home was being used to grow marijuana illegally. NY1's Dean Meminger filed the following report.

Investigators spent a third full day at the site of Tuesday's explosion in the Bronx, but they have reached some initial conclusions about what happened.

"A home in the Bronx used as a marijuana grow farm that exploded this week after an illegal gas hookup leaked and then sparked, killing a highly decorated fire department chief," said Police Commissioner James O'Neill.

FDNY Battalion Chief Michael Fahy was killed by flying debris from the explosion. The city posthumously promoted him to deputy chief Thursday as fellow firefighters and relatives prepared to attend his wake. 

The explosion occurred after firefirghters responded to reports of a strong gas smell coming from the home on West 234th Street in Kingsbridge. The house was already under investigation by police as a possible "grow house" for marijuana. 

"So far as for the crime scene, it is active as of right now. We have recovered an enormous amount of material, pipes and meters that will be taken to Maryland under the ATF and examined for tampering," said NYPD Chief of Department Robert Boyce. "Right now, we are not there with any charges as far as manslaughter. " 

Two men allegedly associated with the house have been taken into custody. Garibaldi Castillo is charged with felony marijuana possession, meaning he had more than 10 pounds of the drug. And a 34-year-old, Julio Salcedo, is expected to be hit with felony marijuana possession as well. 

It's still not clear whether they altered the gas line to assist with growing marijuana, but gas is used to run heaters and other equipment to grow marijuana indoors.

"Dean, there is a structured environment that goes with a grow house that you have to create a high-intensity environment," Boyce said.

Law enforcement sources tell NY1 that tampering with the gas line would enable a grower to avoid suspicion that a lot of gas is being used and avoid paying a high gas bill.

Detectives are still trying to determine what equipment was in the house.