KINGSBRIDGE, Bronx -- The rental house where an explosion Tuesday morning killed an FDNY Battalion chief and injured other firefighters was reportedly the site of a known indoor marijuana growing operation.
It happened inside a two-story private house on West 234th Street in the Kingsbridge section just after 7:30 a.m.
Law enforcement was in the process of investigating the location, where a small group of renters were operating the apparent grow house. One of them may have even been in the house when firefighters arrived to check reports of a gas leak.
PHOTOS: Explosion in the Bronx
Battalion Chief Michael Fahy, a 17-year-veteran with Battalion 19 in the Bronx, was evacuating the house at the time and was struck by debris from the explosion.
Authorities are now actively searching for members of the small group, described as professional dealers who drive luxury cars.
The gas line to the house was apparently capped by firefighters up to 45 minutes before the explosion, so investigators are looking at other options connected to the cause of the explosion.
One possibility is that the blast was electrical in nature, as marijuana growers need high-powered lights kept on around the clock. Heating and air conditioning systems that cool the space down also use large amounts of electricity. But they say portable gas, which is used to manufacture hash oil, could have provided the spark.
The production of the oil -- also known as honey oil, BHO, dab or wax -- requires a butane or propane tank to heat the marijuana plants. THC, the active ingredient in marijuana, is then dissolved from the marijuana leaves and captured as an oily residue that can be smoked with E-cigarettes or cooked into edibles.
The form provides significantly higher concentrated levels of THC than traditional smoking.
Given the explosion that occurred, hash oil production at the home is an avenue under active investigation.
Chemical fertilizers or pesticides, which are usually present in grow houses, would have only increased the force of the blast.
The house had reportedly been on the NYPD's radar.
"A couple of weeks ago, we had information, we were in initial stages of investigation on this block as a possible grow marijuana house," Police Commissioner James O'Neill said. "I'm not going to go too deep into that, based on some preliminary info we had received."
One neighbor who didn't want to be identified told Eyewitness News that he had his suspicions about the home.
"I saw nobody really living in that house," he said. "Just coming and going, in and out, that's what got me suspicious."
The house that exploded was being rented, its landlord owning two other homes nearby. Tenants say he's an excellent landlord who takes good care of his properties. Now, one of his homes is the center of a criminal investigation.
Investigation: Bronx explosion could be linked to pot growing operation