State and local law enforcement officers raided Thursday an illegal marijuana garden estimated at 32,000 plants -- worth $128 million -- on Hidden Villa land, although the non-profit camp and nature center in Los Altos Hills was not aware of them, said Santa Clara County Sgt. Ed Wise.

The plants, ranging from 2 to 4 feet tall, extended over several acres of steep, remote hillsides and canyons near the intersection of Page Mill and Moody roads, Wise said.

He said the garden was located such that it would not have been encountered by campers or recreational visitors to Hidden Villa, an environmental education nonprofit.

Deputies spotted the plants during a targeted aerial survey last week, Wise said. From the air, marijuana appears a bright, florescent green compared to the darker green of natural brush, he said.

Early this week, the Marijuana Eradication Team sent in a tactical ground team to confirm the finding. The size of the garden grew from earlier estimates as deputies traced irrigation lines which linked to other areas, Wise said.

Early Thursday morning, deputies, Palo Alto police officers and California Fish and Game officers seized control of the garden in a "very covert and tactical" raid, Wise said.

The officers were on the lookout for suspects, booby traps and other dangers. No one was spotted at the garden, however, he said. Once established, marijuana gardens are highly automated, Wise said.

Deputies did find a firearm that looked as if it was left recently, he said.

The growers had cleared all low-lying brush from the area but left taller plants standing, Wise said. They applied fertilizer, pesticides and had automated irrigation, he said. He did not know the source of the water.

The marijuana plants, which were nearly ready to harvest, will be destroyed, Wise said.

The eradication team does not have the manpower to conduct extensive searches for the growers, who are often hired laborers, not the masterminds behind the operation, Wise said.

The garden is estimated to have been there for at least a month. Wise said he did not know if it had been used for marijuana growth previously.

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