AUGUSTA — Maine’s top marijuana regulator said the state has few tools to prevent medical marijuana from being sold on the black market.

Most caregivers are following the rules, but economics are driving the illicit sale of marijuana, said Erik Gundersen, director of the Maine Office of Marijuana Policy.

“It’s an economics thing. You can do quick, back-of-the-napkin math,” Gundersen said. “I would imagine it’s easy to veer into the more gray area.”

The Maine Legislature’s Marijuana Advisory Commission met Tuesday for the first time since federal prosecutors alleged that a medical marijuana operation illegally sold more than $13 million in weed, the Bangor Daily News reported.

A federal grand jury Tuesday indicted 11 of 12 defendants charged in an illegal marijuana distribution and money laundering scheme in the Franklin County area, the Sun Journal reported.

The Office of Marijuana Policy has fewer ways to regulate the medical marijuana market than the recreational market for which retail sales started just last year, Gundersen said.

The office proposed a “seed-to-sale” tracking system as part of a larger attempt to regulate the medical marijuana industry but those rules were rejected by lawmakers.

Scott Gagnon, public health representative for the Marijuana Advisory Commission, was not surprised by the illicit market for medical marijuana.

“It’s been weakly regulated at best,” Gagnon said of Maine’s medical marijuana industry. “The ingredients are all there for this to be able to happen.”