DENVER, Colo. (CBS4) – A total of 32 people have been arrested and 20,000 marijuana plants seized in a series of raids on illegal marijuana cultivation sites around Colorado.

The raids of pot grows on public lands were conducted by federal and local law enforcement agencies over the last six weeks in counties across the state including Jefferson, Montrose, Fremont and Routt.

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(credit: usdoj.gov)

(credit: usdoj.gov)

Such grows are a major concern for the U.S. Attorney’s office and other federal authorities who warned that Colorado’s legal marijuana industry would be tolerated, but only under certain conditions.

(credit: Bureau of Land Management)

(credit: Bureau of Land Management)

One of those raids was on Bureau of Land Management land along the Dolores River near Gateway on Colorado’s Western Slope. One Honduran and five Mexican nationals were arrested. Some 70 pounds of processed marijuana was still on site.

A second illegal grow was discovered near the first site in Mesa County.

(credit: usdoj.gov)

(credit: usdoj.gov)

Other raids included:

– Aug. 19 in the Pike National Forest
– Aug. 28 the Routt National Forest in the Buffalo Pass area
– Sept. 1 near Cotopaxi and Westcliffe, where 20 people were arrested and 28 firearms taken
– Sept. 7 on Cordova Pass near Trinidad

The Department of Justice previously set eight areas that federal prosecutors would go after even with Colorado’s state legalization of pot. One of those areas was the growing of marijuana on public lands.

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U.S. Attorney for Colorado John Walsh says these raid represent a new phase to destroy the effort of drug trafficking organizations to use Colorado as a source state for illegal marijuana around the country. He believes it is the work of groups outside the U.S.

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(credit: usdoj.gov)

(credit: usdoj.gov)

“We have concern on law enforcement drug trafficking organizations from Mexico are involved in growing marijuana here in Colorado,” said Walsh.

Such operations are not new. CBS4’S Rick Sallinger obtained video for one discovered in the Colorado mountains five years ago. Whoever was involved in that grow left in a hurry, leaving behind their video game, cooking stove, irrigation system and makeshift pond to catch water.

(credit: usdoj.gov)

(credit: usdoj.gov)

What has changed in that time is the emergence of a recreational pot industry that may have given some the sense that illegally growing marijuana in Colorado is safe from prosecution.

Walsh wonders if that gave a sense of comfort to the illegal growers, “Outside drug trafficking organizations may come to Colorado with the notion it may go unnoticed because of the amount of marijuana activity.”

(credit: usdoj.gov)

(credit: usdoj.gov)

In many cases hikers or federal rangers discovered the illegal grow operations. State and local agencies assisted in the busts. The marijuana seized in those raids was bundled and sent off for destruction.

(credit: usdoj.gov)

(credit: usdoj.gov)

It wasn’t just a matter of seizing the pot and making the arrest. The ground the pot was grown on will have to be reclaimed because there is danger the plants were contaminated with dangerous pesticides.

(credit: Bureau of Land Management)

(credit: Bureau of Land Management)

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CBS4’s Rick Sallinger is a Peabody award winning reporter who has been with the station more than two decades doing hard news and investigative reporting. Follow him on Twitter @ricksallinger.