personnel. make sure there s no dangerous people in there. nobody harmed. reporter: check this out. this is a trip wire connected to beer bottles. if somebody comes into the grow and doesn t see this thing, whoever is out here is going to know about it. looks like they got most of it before you got here, but this is the last plant left? just about. the helicopter flew yesterday. they probably made a priority to get it out of here. reporter: it is estimated california produces eight times more pot than is consumed here. most is trafficked across america. today, could be up to 80% of the black market weed consumed in the u.s. these are some big ones in here. see a bunch up there. a second grow site, we found absolutely massive illegal plants. so what do you think, this is probably eight feet tall, right? about that. reporter: full irrigation system in here. you have standard drip line that you ll see in people s landscape, in their backyard. looks like this is their camp area
when the sale of recreational pot becomes legal in california in january, the state will become, by far, the largest legal marijuana economy in the nation. it doesn t mean all marijuana there will be for legal purposes. we got a firsthand look at the efforts to nip the pot black market in the bud. reporter: in the foothills of the sierra, a narcotics task force is preparing for a raid. they re not going after heroin, cocaine or meth. they re looking for p ining for. how many of these are protected? a portion of them. always worried about getting ripped off by people looking to steal their crop. we ve had a lot of shootings in this county. reporter: in january, california will become home to the nation s largest legal pot industry, but the state s black market weed will still be a far bigger business. what are they looking for inside the shed? just clearing it for