Cannabis worth up to £148,000 was seized by police during an Oldham drug raid last week.
Two men were arrested on suspicion of the production of cannabis and abstracting electricity as officers discovered 295 plants in five steel containers.
A warrant was issued on May 31 as part of Operation Caminada at an industrial estate on Hargreaves Street, Westwood, and two cars were seized.
Chief Superintendent Tim Forber, divisional commander for Oldham, said: "These arrests prove that we are continuing with our fight against organised crime and is another excellent result.
"This criminal endeavour was particularly dangerous as the offenders had connected directly to the national grid to illegally bypass the electricity supply – a reckless act which could have put themselves, and others, at risk.”
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A grey Mercedes E class car and white BMW 1 Series were seized at the site and a 48-year-old man and 52-year-old man were arrested.
Both man were released on bail pending further inquiries until September 19.
Further warrants were conducted at properties in Deansgate, Manchester, and Worsley, Salford, where computer equipment and around £2,000 in cash was seized.
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Chief Superintendent Forber added: "I cannot stress how important it is that members of the public continue to support us and provide information. If anyone knows anything about those involved in drug or any other criminal activity I would urge them to get in touch."