The dozen portable huts of the grow-op contained fairly sophisticated light and watering systems, police say. (RCMP)

RCMP in High Prairie, Alta., have seized an estimated $6.5-million worth of marijuana and charged six men in a bust of a large grow-operation.

Plants in various stages of growth were found in 12 portable semi-circular huts, each 60 metres long, six metres wide and three metres high. The 6,500 plants were being grown on a property about 15 kilometres north and 13 kilometres west of High Prairie.

Investigators who swept in last Thursday described the operation as fairly sophisticated in terms of concealment, location, watering and light-control systems. The suspects had built two living and cooking structures on the site.

Police arrested six men at the scene, between the ages of 25 and 45, and they remain in custody. They face charges of producing marijuana, possession of marijuana for the purpose of trafficking and possession of a stolen water pump.

Police estimate the street value of the crop at $6.5 million, one of the largest seizures in Alberta to date.