DECKERS, Colo. -- It's rare to see a Black Hawk helicopter loaded with bushels of marijuana fly off from Colorado's Foothills but that's exactly what happened Friday when federal and local law enforcement agents confiscated roughly 30,000 marijuana plants growing among pine trees in the Pike National Forest.

All day Friday, a Black Hawk helicopter with the Colorado Army National Guard lifted bundles of marijuana out of the forest to a road where the plants were loaded into dump trucks. The plants, which filled two dump trucks, will be driven to an undisclosed location and destroyed.

The marijuana plants were growing near Highway 126, south of Buffalo Creek, about 7 miles north of Deckers, in Jefferson County. They have a street value of tens of millions of dollars.

The operation discovered Friday is six times larger than the one that was found on July 9, also in the Pike National Forest.

In that case, the local and federal agents spent more than 24 hours clearing a marijuana growing operation of more than 5,100 marijuana plants. Those plants weighed nearly 2,000 pounds and had a street value of $2.5 million.

Marijuana costs roughly $3,000 a pound, and each one of the plants discovered Friday was more than one pound each, including the stalk and leaves.

Drug agents at the scene told 7NEWS they suspect that the grow is part of a Mexican drug operation. Drug dealers are finding that there's too much pressure at the border and it's easier to grow the marijuana inside the United States and transport it elsewhere, than to take it across the border.

Undetected marijuana farms are a growing problem for the U.S. Forest Service because these extensive grow operations often have elaborate irrigation systems and the growers use pesticides and fertilizers on the plants that could seep into the water. The operation is about 1 mile away from the South Platte River, a source for Denver's drinking water.

Officers with the U.S. Drug Enforcement Agency, the U.S. Forest Service, Immigrations and Customs Enforcement, Jefferson County Sheriff's Office, Douglas County Sheriff's Office and the Colorado Army National Guard are all involved in the operation. They've been investigating for two months.

The person or persons responsible for the marijuana farm is still not known. Authorities said that a person keeping watch on the plants ran off when officers swarmed in Friday morning.