BANGOR — Three men charged in one of the biggest marijuana busts in Maine history — a sophisticated operation nestled in the Down East woods that featured bunk houses, a warehouse and a fenced-in compound — were convicted by a federal jury Friday.

Jurors found Malcolm French, of Enfield, Rodney Russell, of South Thomaston, and Kendall Chase, of Bradford, guilty of conspiracy counts related to the marijuana-growing operation. French and Russell also were convicted of manufacturing drugs, harboring workers who entered the country illegally, and additional drug-related charges.

Prosecutors said the three men played key roles in the sophisticated operation in the woods of Township 37. Federal prosecutors said marijuana was grown and stored with the help of migrant workers.

Assistant U.S. Attorney Joel Casey said the operation was so well-concealed that a game warden tipped off about the operation rode right past it the day before it was discovered by law-enforcement aircraft.

“He drove right past it on his ATV. It was very well hidden,” Casey said Friday evening after the verdicts. “It was camouflaged with tarps and camouflage paint.”

The jury also returned a guilty verdict against Haynes Timberland Inc., the company owned by French and his wife, Barbara Haynes French, of Enfield, which owned the land in Township 37. Forfeiture proceedings were being discussed after the verdicts in U.S. District Court.

Defense lawyers expressed disappointment with the verdicts that followed a nearly three-week trial. At least one of the defense attorneys vowed to appeal.

State police said a raid at the Washington County site in September 2009 yielded 3,000 plants worth an estimated $9 million, making it the second-largest pot bust in state history.

A Mexican man accused of overseeing the operation pleaded guilty last summer and another man also pleaded guilty before the trial began. Faced with testifying before a grand jury, another man implicated in the operation killed himself in 2011 at a location not far from the marijuana operation.

Casey credited law enforcement officials, in particular the Maine Drug Enforcement Agency, for helping to unravel a complicated operation.

“It was a very complicated case but the evidence didn’t lie and the jury obviously followed the evidence very closely,” Casey said. “It was a 3½-year investigation. There was a lot of evidence but it all pointed to one inescapable conclusion.”