DENVER -- The investigation into Wednesday's explosion at a marijuana grow house continues and we've learned there were no legal permits for the activities taking place inside the building.
We've also learned this isn't the first case of its kind recently that Denver Fire investigators have looked into.
The fire in southwest Denver burned intensely. Torched butane bottles are scattered everywhere. Witnesses say three people ran from the explosion screaming. The three people were burned and all had to go to the hospital.
Fire officials said Thursday they suspect two crimes happened. One was an illegal marijuana grow operation inside the vacant building. "There were not permits for that operation at that address," says Denver Fire Department spokesman Brian Lukas.
Investigators say the second was an illegal extraction process that caught fire out back. There were dozens of bottles of butane that fed the fire and explosion.
The Denver Fire Department says firefighters are encountering more of these fires as more people try to cash-in on the growing marijuana edible industry.
Last May they responded to a grow house for a similar fire and just last month the arrested three people after an extraction fire at a home on Julian Street.
The extraction process is done to get the oil that marijuana edible makers use to give the products their potency. But it's a dangerous process.
Neighbors said Wednesday they never really knew for sure what was happening in that building, but they say they did joke about a marijuana operation taking place.
Law enforcement says if you suspect an illegal operation, don't hesitate to call them.
Police say the owner of the building where the explosion happened Wednesday was in the process of obtaining permits.
Investigators turned the building back over to its owner Wednesday night, but since police say the operation was illegal, they seized the plants that were inside.
The conditions of the three people hurt were not released.