In this Oct. 10, 2016 photo, the morning sun rises behind a row of maturing pot plants at Los Suenos Farms, America's largest legal open air marijuana farm, in Avondale, southern Colo.

Associated Press

Authorities say federal agencies removed more than 71,000 marijuana plants from public lands in Colorado last year.

The Denver Post reports the plants were grown illegally on about 38 acres in the state during the growing season that usually runs from early summer through the fall.

According to the U.S. Attorney's Colorado office, at least seven cases resulted in prison time from related investigations that involved the U.S. Forest Service, Bureau of Land Management and Homeland Security Investigations.

Authorities found about 5,000 pounds of trash and infrastructure at each illegal grow site in the San Isabel National Forest. They also found man-made reservoirs and numerous structures, as well as pesticides and other chemicals that required hundreds of hours of cleanup.

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