SEQUOIA NATIONAL FOREST, California (CNN) -- Beyond the towering trees that have stood here for thousands of years, an intense drug war is being waged. Illegal immigrants connected to Mexico's drug cartels are growing hundreds of millions of dollars worth of marijuana in the heart of one of America's national treasures, authorities say. It's a booming business that, federal officials say, feeds Mexico's most violent drug traffickers. "These aren't Cheech and Chong plants," said John Walters, director of the National Drug Control Policy. "People who farm now are not doing this for laughs, despite the fact Hollywood still thinks that....