FARMINGTON – Police arrested a Farmington man after a marijuana growing operation was found in his home at 401 Farmington Falls Road on Friday.

Gary O’Brien, 50, was arrested on charges of cultivating marijuana and trafficking schedule Z drugs, said Gerry Baril of the Maine Drug Enforcement Agency on Monday.

A search warrant was obtained after a six- to eight-month investigation that included surveillance and background checks, he said.

MDEA agents were joined by Farmington police, Franklin County Sheriff’s Department officers and state police for the home search around 9 a.m. Friday, Baril said.

In the basement, police found 15 plants, not quite mature, and five others in a nursery or early stage, he said.

Along with the 20 plants, they found 400 grams or just under a pound of dried, processed marijuana, resulting in the misdemeanor trafficking charge, he said.

The 15 plants were in a hydroponics system that includes a series of pumps to move nutrients to the plants. The five smaller plants were believed to have been cuttings from mature and harvested plants, cloned to reproduce the same species, he said.

The investigation was undertaken by the agency after a citizen provided information to a state trooper and Franklin County deputy whom he happened to run into having lunch, Baril said. They forwarded the information to MDEA.

O’Brien was released from Franklin County Detention Center on $5,000 unsecured bail for a court appearance on April 24.