Narcotics agents arrested three people and seized 2,200 high-grade marijuana plants worth $8 million, some as large as small trees, in a raid Wednesday on a sophisticated indoor farm, authorities said.

"When you've got marijuana of this quality, it's not destined for the street corner," said Lt. Patrick Kerins, a spokesman for the San Diego Narcotics Task Force. "It's probably destined for delivery throughout the U.S."Kerins said the seizure was the largest of any indoor marijuana-growing operation in county history.

He said the operation had set up shop in a huge downtown warehouse, where plants were laid out in neat rows under bright lights. Hoses and drip lines fed liquid fertilizer to the plants and carbon dioxide was pumped into the room to promote plant growth.

Agents arrested Gary Clamp, 50, suspected of being the leader of the operation, Karol Zunino, 45, and Darryl Miller, 31, all of San Diego.

A spokesman for the U.S. marshal's office said charges of possession of a controlled substance and conspiracy to manufacture and distribute a controlled substance would be brought against the three.