The leader of the largest indoor marijuana growing operation in Berkeley history pleaded guilty Monday to charges that he had been cultivating plants in a Berkeley warehouse for three years, United States Attorney Joseph Russoniello announced in a statement.

Joshua Hedlund, 31, pleaded guilty to charges that he grew the marijuana and used the profits to pay the warehouse mortgage, the report said.

"This was the largest marijuana grow that we had been involved in in the history of the department," said Berkeley police Sgt. Mary Kusmiss.

In March 2006, Berkeley police officers uncovered an operation on the 800 block of Allston Way. There, they discovered 2,700 marijuana plants ranging in size from seedlings to mature plants, 114 pounds of processed marijuana weighed and packaged for sale, $220,000 in cash and 12 guns, including an assault rifle, Kusmiss said.

"The proceeds would be in the millions of dollars at the street level," she said.

As part of his plea, Hedlund will hand more than $1 million over to government officials.

He will be required to surrender more than 7,000 acres in Humboldt and Trinity Counties and open 5,000 more acres spanning Humboldt and Mendocino counties to police search, according to the statement.

Combined, the charges can carry up to twenty years in jail and a fine of $500,000. Hedlund will appear in court again on May 16 for sentencing.