Three people have been arrested after police in Somerset County busted a large and well-organized marijuana operation.

Huansheng Mai, 75; Yuling Mei, 63; and Yiming Hu, 68, have been charged with illegal marijuana cultivation and unlawful trafficking in scheduled drugs with more than 500 plants, according to the Waterville Morning Sentinel.

Somerset County Sheriff Dale Lancaster revealed the bust during a Wednesday county commissioners meeting. He described the operation as “very well-organized” and said that the arrests came after a yearlong investigation, the Sentinel reported.

When police raided the West Ridge Road residence in Cornville, they found 750 marijuana plants and 90 pounds of processed marijuana, according to the newspaper.

The sheriff’s office said mid-day Thursday that the marijuana was worth an estimated $200,000.

Lancaster pledged to be “more aggressive” in deterring illegal marijuana operations within his county.

Those arrests come just weeks after police busted two other large illegal marijuana operations in neighboring Kennebec County. In Belgrade, police arrested two people and seized 2,300 marijuana plants on Jan. 2, while in the town of China, three people were arrested and police seized 970 plants and many more seedlings on Dec. 30.

Those are just the latest large-scale illegal marijuana operations uncovered in the past year. They received greater scrutiny after the Penobscot County Sheriff’s Office found an illegal marijuana operation in Carmel, where police seized 3,400 plants and 111 pounds of processed marijuana. Since then, other large illegal marijuana operations have been found in Dexter, Wilton, Machias and other communities.

A leaked federal government memo, first obtained by the conservative Daily Caller and published in August, estimates Maine has 270 large-scale illegal marijuana grows connected to organized crime groups in China. The memo’s authors note that the money may be used to further crime in the U.S. or be sent back to China.

Similar operations have been found in California, Oklahoma and Oregon.

In response, Maine’s congressional delegation sent a letter to U.S. Attorney General Merrick Garland, calling on the Department of Justice to crack down on such illegal marijuana operations.

It’s not yet clear whether the illegal marijuana grow uncovered in Cornville is connected with these other operations or to the crime network described in the federal memo.