Kay County Deputy Bill Grose grimaces as he opens the valve on an anhydrous ammonia tank in rural Kay County near Blackwell and Newkirk, to demonstrate the fumes generated by the chemical. Meth makers use anhydrous ammonia to convert pseudoephedrine from cold medicine into a methamphetamine base. Officers have caught a few anhydrous ammonia thieves because they passed out after breathing too much of the vapor. (AP Photo/Sue Ogrocki)

Law officers with night-vision goggles lurk behind trees and giant hay bales hoping to catch the crooks, but there are only a handful of deputies and hundreds of square miles of farmland.

Kay and Noble counties have 17 anhydrous ammonia co-ops, and many farmers keep their own tanks. Thieves have struck an anhydrous ammonia pipeline from Enid to Tulsa so many times, workers buried the line's sample sites and removed release valves.

Signs posted along the pipeline and near tanks warn the area is under surveillance by the district attorney. It doesn't seem to matter.

One Noble County test site was buried with rocky cement, but inch by inch, thieves are scraping a hole in the hard mound.

"They're probably too scared to stay very long with cars driving by," said Chad VanHoesen, part of a five-member drug task force for Kay and Noble counties. "They're real spooky."

A 2000 law made it a crime to tamper with anhydrous ammonia tanks. Lawmakers later added pipelines.

Law officers have seized about 50 meth labs in Kay and Noble counties during the last year _ most of them in the parking lot of Wal-Mart, this rural area's shopping hub.

Narcotics agents spend hours in Wal-Mart stores looking for people buying or stealing meth ingredients, including cold medicine, lithium batteries, lighter fluid and drain cleaner. They've also trained Wal-Mart employees to spot meth cooks.

"You can go buy everything you need at Wal-Mart or a hardware store," narcotics officer James Leone said. "We basically go from lab to lab, 24-seven."

Meth makers use anhydrous ammonia to convert pseudoephedrine from cold medicine into a methamphetamine base.

Addicts fill coffee thermoses and even 20-ounce convenience store mugs with anhydrous ammonia, then park and cook their drug before the fertilizer evaporates. Residents find empty pill blister packs on the roadside.

Officers have caught a few anhydrous ammonia thieves because they passed out after breathing too much of the vapor.

Meth hit hard in Oklahoma about five years ago. In 1997, Leone's group busted eight labs. The next year they got 48.

Kay County Deputy Bill Grose, who has busted 30 meth labs in the last two years, has resorted to sneakiness to catch anhydrous ammonia thieves.

He sticks bits of rags in tank valves and sprays tank trailer tires with Armor All so he can detect footprints. He checks on the tanks every few hours so he'll know what time of day crooks are stealing.

The deputy often creeps down dusty, potholed roads at night with the lights off on his patrol cruiser.

"It never slows down _ snow, sleet, rain _ it doesn't matter to them," said Grose, who pulls the graveyard shift.

He's convinced meth addicts are doing counter-surveillance on him with their own police scanners. Sometimes, he has the dispatcher give him a fake call on the radio so the thieves will think he's left the area.

"I'm not going to catch them all, but I don't want them to be comfortable," Grose said. "I want them sneaking."

In this part of Oklahoma, a motorist in an unknown vehicle is presumed lost or up to no good.

Williams notices the strange vehicles prowling around his farm and spies the bits of hose lying near his storage tanks. He knows better now not to leave tools near the tank _ he's lost too many that way.

"It's a pretty big nuisance," he said, standing in a field in dusty Wranglers and a ball cap. "You would like to leave your stuff set on your own property and not have it messed with just for the sake of somebody mashing up some cold tablets to get high with their friends."

Some farmers chase after anhydrous ammonia thieves, though law officers don't encourage it.

A farmer driving a tractor through a Kay County cotton field had to duck for cover from rifle fire in July when he tried to get a glimpse of a thief's license plate.

Williams put a taller barbed-wire fence around his tank. He calls narcotics agents when he sees thieves, but he doesn't confront them.

"You never know if they're high or what," he said. "You never want to endanger yourself."

He let his anhydrous ammonia tank go empty this winter to keep the thieves away. Farmers normally keep tanks full year-round, buying ammonia when it's cheapest at the local co-op. They put it in the soil in August and September.

Williams now dreads fertilizing season, when he expects droves of drug addicts to invade his normally quiet country life.

He worries what will happen if, one day, he startles a weapon-toting thief, or if children playing in out buildings stumble on the toxic leftovers of a meth lab.

"It kind of makes the country a dangerous place," he said.