BANGOR, Maine — A fifth man has pleaded not guilty to charges in connection with a marijuana growing operation in Washington County that law enforcement officials have called the largest in the state’s history.

Moises Soto, 52, of Nuevo Leon, Mexico, pleaded not guilty Monday in U.S. District Court to one count each of conspiracy to manufacture 1,000 or more marijuana plants and manufacturing 1,000 or more marijuana plants, two counts of maintaining a drug-involved place and three counts of harboring illegal aliens, according to information filed on the court’s Electronic Case Filing system.

He was arrested March 15 at the McAllen, Texas, Port of Entry, according to court documents. He allegedly ran the growing operation using undocumented workers.

Soto agreed to be held without bail pending the outcome of his case. He and the other defendants are scheduled to be tried in federal court in Bangor on Sept. 4, according to the U.S. Attorney’s Office.

Also awaiting trial are Robert Berg, 49, of Dexter; Malcolm French, 50, of Enfield; Rodney Russell, 48, of South Thomaston; and Kendall Chase, 55, of Bradford. All four men, who are free on bail, along with Haynes Timberland Inc., a Maine corporation, have pleaded not guilty to charges stemming from the Sept. 22, 2009, seizure of 2,943 marijuana plants.

It took more than 60 state and federal law enforcement officers almost a week in the fall of 2009 to harvest the high-quality marijuana plants worth an estimated $9 million from a remote area in Township 37, near the town of Wesley and about 10 miles off Route 9, according to previously published reports.

The massive pot plantation was found after a tip was left on the Maine State Police Troop J website, according to the U.S. Attorney’s Office. When police flew a plane over the site, people on the ground set fire to several buildings being used as dormitories before the suspected growers fled.

When the marijuana operation was discovered, Maine Drug Enforcement Agency officials characterized the size, scope and detail of the operation as quite surprising. They said the plants — many of them 8 feet tall and highly cultivated — were of extremely high quality.

“We have never seen this type of operation in Maine before,” MDEA Director Roy McKinney said in 2009. He confirmed that it was a plantation or farm, where caretakers of the crop lived 24 hours a day, seven days a week.

Earlier this month U.S. Magistrate Judge Margaret Kravchuk ordered a former worker be detained as a material witness, according to information filed on the court’s Electronic Case Filing system. Martin Roblero, 21, of Mexico is expected to be called as a witness at the defendants’ trial. He was working at the grow site in the summer of 2009, according to court documents.

“After fleeing the grow and being spirited out of Maine, [Roblero] eventually made his way to the Indianapolis area,” the motion for his detention dated Feb. 20, said. “He was subsequently arrested for and convicted of child molestation.”

Information about the circumstance of that case was not included in court documents filed in Maine. Roblero was due to be released on March 3 and deported to Mexico the following week.

He was granted immunity in exchange for his testimony in the Maine case.

Information about whether he is now in Maine or where he is being held was not available Monday morning.

If convicted, defendants charged with conspiracy and manufacturing marijuana face between 10 years and life in prison and a $10 million fine.

Those charged with managing and controlling property used to manufacture marijuana face up to 20 years in prison and a $500,000 fine, if convicted. Defendants charged with harboring illegal aliens face up to five years in prison and a $250,000 fine; and those charged with assisting individuals to evade apprehension face up to 15 years in prison and a $5 million fine, if convicted.