Maine is the newest frontier for the illicit marijuana trade, with potentially hundreds of suspected unlicensed grow houses operating in the state, a CBS News investigation has found. 

It's part of a larger phenomenon nationwide. Thousands of illegal marijuana farms have been cropping up in states like Oklahoma, California and Colorado, according to Raymond Donovan, the former chief of operations for the Drug Enforcement Agency.

"[Maine] is a perfect location to cultivate cannabis and do it in a way that is very discreet," Donovan told CBS News. In part, that's because of the state's proximity to major distribution markets in Boston and New York. 

In December, after a six-week investigation, Maine law enforcement raided a home in Machias, a rural town on the southeastern coast, and found a large facility with over 2,600 plants and 100 pounds of processed and packaged marijuana. 

"I've been doing this a lot of years, and that was probably the biggest indoor marijuana grow I've ever seen," Police Chief Keith Mercier said. "It was quite an impressive operation."

Machias Police were assisted by DEA, FBI, Homeland Security, the Office of Cannabis Policy, Maine Drug Enforcement Agency and the Washington County Sheriff's Department.

"This is a statewide problem," Mercier said. "The information we have says that there's over 200 (facilities) that are actively working right now."

Maine law enforcement has executed search warrants at at least 34 properties tied to illicit marijuana since last June, and investigations continue. 

But the biggest surprise in the proliferation of illegal growing in secluded stretches of Maine may be who's believed to be backing the operations.

"Chinese organized criminal networks that are international by nature are behind some of the biggest black market marijuana trafficking organizations that we've seen to date," Donovan said.

In February, 50 U.S. lawmakers wrote to Attorney General Merrick Garland demanding answers about China's role in illicit marijuana nationwide.

"We are deeply concerned with reports from across the country regarding Chinese nationals and organized crime cultivating marijuana on United States farmland," the bipartisan group wrote. 

Donovan said the easiest way to spot an illegal marijuana crop is the amount of electricity it uses, which Maine native Steve Robinson, editor of the Maine Wire, has been tracking. Robinson has compiled a database of suspected illegal cannabis cultivators around the state. 

"These locations consume huge amounts of electricity," he told CBS News. "In order to accommodate that amount of energy, you need to upgrade your electrical infrastructure — and significantly. We're getting into specialty electrical equipment that is very scarce and hard to come by, especially in the state of Maine."

Mercier says he used one of Robinson's articles as a training tool in what to look for before executing the search warrant at the Machias property.

"Once we subpoenaed the power records from the power company, [it] was pretty hard to explain why somebody anywhere would be using that amount of power," he said.

Mercier said the Machias operation was using four to five times the amount of power that a normal residence would use. Other telltale signs included shuttered windows and complaints from neighbors about pungent smells and suspicious vans coming and going. 

During the operation, three men were arrested and charged with unlawful cultivation. Police found a Malaysian passport, a Chinese passport and a Brooklyn driver's license at the scene.

Donovan told CBS News that some of the people working in marijuana grow operations around the country are Chinese nationals who are victims of labor trafficking. 

"[They're] brought here under the auspices that they're working under a legit business," he said. "And they're often kept unwillingly in these locations and told what to do to oversee the cultivation of these marijuana plants." 

"They were being paid $1,000 a month to work 24/7," Mercier said. "I wasn't left under the impression that any of these gentlemen were in charge of anything. They were just strictly there to maintain the product."

Some of the same criminal groups behind illicit marijuana participate in a far deadlier drug trade, according to Donovan and other law enforcement sources. Donovan said the DEA first connected Chinese organized crime to these illegal weed cultivators by following the fentanyl supply chain. 

"We quickly realized that money from selling fentanyl on the streets was going back to Chinese money brokers in Brooklyn and in Queens," he said. "We started investigating many of these brokers [and] observed that they were also trafficking in marijuana."

Marijuana remains illegal under federal law, but a majority of Americans now live in states where it's legal. There is a robust market for illicit marijuana — state regulations allow the sale of marijuana, but demand outstrips supply, opening a market for illegal growers. 

Donovan fears that less prosecution will encourage organized crime groups trafficking marijuana to infiltrate sparsely populated states. 

"If you have a place like Maine where marijuana is legal, there is less scrutiny on marijuana" he said. "It's a recipe for disaster in the sense that they're going to continue to go to these places and cultivate."

In:
• Marijuana
• China

Nicole Sganga

CBS News reporter covering homeland security and justice.

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