PASCO, Wash. (AP) – Washington state authorities have seized 70,000 illegal marijuana plants from farmers’ fields this year after they were detected growing with other crops.

Tri-City Herald reported Thursday that Franklin County deputies have discovered illegal operations using airplanes and drones to find darker marijuana plants among lighter foliage, mostly cornfields.

Authorities say growers have hidden their prohibited crop among legal commodities for years and remove the pot plants before farmers harvested their own crops.

Authorities say it remains illegal to grow marijuana in the county under a ban imposed by county commissioners.

Authorities say 500 pounds (227 kilogram) of processed cannabis ready to be sold was discovered this month and another 26,000 plants were found this week across the county.

Information from: Tri-City Herald,