Authorities who spent the past decade targeting marijuana growers in the Sierra Nevada wilderness have turned their attention toward California's agricultural heartland -- the nation's richest farmland -- which they say is the new hot spot for illicit growers, their guns and toxic pesticides thanks to medical marijuana laws.

At a news conference Wednesday, authorities announced results of a summer-long enforcement effort in the state's agricultural region: 175 local and federal arrests, along with 100 guns, $4,869 in cash and 400,000 plants seized across hundreds of thousands of acres.

"These grows are not about medical marijuana," said U.S. Attorney Benjamin Wagner. "They are large amounts cultivated for commercial purposes and sold to people often outside of California."

"Make no mistake: This isn't about medicine. This is about money," Kern County Sheriff Donny Youngblood said. "Almost every grower we take down has some connection to a cartel in Mexico. They aren't here to make a little money. They are here to make a lot of money."

For more, see: Authorities target pot grows on Calif. farmland