TULSA, Okla. (AP) -- Just when Oklahoma finally found a way to put its homegrown methamphetamine labs out of business, drug agents began finding more meth from Mexican cartels on the street.

Oklahoma's meth lab seizures have fallen 90 percent since April 2004, when it became the first state to ban over-the-counter sales of everyday cold and allergy medications that can be converted into methamphetamine in makeshift labs.

But at the same time, seizures of smokeable Mexican meth known as "crystal ice" rose nearly fivefold, from 384 cases in the 15 months before the law to 1,875 since.

Mexican cartel cell groups that traditionally focused on trafficking cocaine, heroin and marijuana have added methamphetamine to their supply, said Lonnie Wright, director of the Oklahoma Bureau of Narcotics and Dangerous Drugs Control.

"We're regrouping and we're kind of at a crossroads," Wright told members of the Oklahoma Sentencing Commission this month. "I think we're through with meth labs, at least for now."

Other states that have copied Oklahoma's anti-meth approach expect to see a similar tradeoff. But drug agents say they can fight ice with techniques they already employ against cocaine and other organized drug trafficking.

"Clandestine labs are like forest fires cropping up all over the state," said Jennifer Johnson, spokeswoman for the Tennessee Bureau of Investigations. "When you have something that's big and contained, at least you can fight it in the same way you always have."

Better enforcement may account for part of the jump in seizures of ice.

Before the state put pseudoephedrine tablets behind pharmacy counters, police and sheriff's deputies' days were consumed trying to find and stop the small labs where meth makers used items as common as rock salt, battery acid and drain cleaner to turn the cold medicine into powdered meth.

The volatile labs posed a threat to the cooks' neighbors, their own children and anyone who happened to stumble into the toxic mess.

Investigators who once lost a minimum of four hours on "small, nothing labs" while working in clumsy decontamination suits are now free to cultivate informants, perform surveillance and target organized trafficking rings, said Oklahoma City Police Lt. Tom Terhune.

Oklahoma's success in closing up its clandestine kitchens prompted more than a dozen other states to follow suit with similar limits on pseudoephedrine. Congress is mulling federal restrictions on the nasal decongestant, found in common medicines such as Sudafed and Nyquil.

Many of those laws have been in effect just a few months and some states say it's too early to gauge the effect. But officials in Iowa and Arkansas are already reporting anecdotal evidence that ice trafficking is on the rise as labs decline.

"If you're a meth addict you either throw in the towel and go into treatment, or you scramble to find some other way to get it," said Curt Smith, assistant director of programs for Iowa's Office of Drug Control Policy in Iowa.

Tennessee, where meth lab seizures have fallen 50 percent since the pseudoephedrine ban took effect March 31, hasn't seen an increase in ice trafficking. But Johnson said agents at a conference last week talked about preparing for it.

"We anticipate if people can't make it at home, we're going to see them trying other ways to get it," she said.