An A.P. investigation into the fallout from those meth fighting laws that restrict the sale of cold medication has turned up results that "surprised" law makers and law enforcement officials:

But an Associated Press analysis of federal data reveals that the practice has not only failed to curb the meth trade, which is growing again after a brief decline. It also created a vast and highly lucrative market for profiteers to buy over-the-counter pills and sell them to meth producers at a huge markup.

In just a few years, the lure of such easy money has drawn thousands of new people into the methamphetamine underworld.

"It's almost like a sub-criminal culture," said Gary Boggs, an agent at the Drug Enforcement Administration. "You'll see them with a GPS unit set up in a van with a list of every single pharmacy or retail outlet. They'll spend the entire week going store to store and buy to the limit."

Inside their vehicles, the so-called "pill brokers" punch out blister packs into a bucket and even clip coupons, Boggs said.

In some cases, the pill buyers are not interested in meth. They may be homeless people recruited off the street or even college kids seeking weekend beer money, authorities say.

But because of booming demand created in large part by the tracking systems, they can buy a box of pills for $7 to $8 and sell it for $40 or $50.

The tracking systems "invite more people into the criminal activity because the black market price of the product becomes so much more profitable," said Jason Grellner, a detective in hard-hit Franklin County, Mo., about 40 miles west of St. Louis.

"Where else can you make a 750 percent profit in 45 minutes?" asked Grellner, former president of the Missouri Narcotics Officers Association.

Since tracking laws were enacted beginning in 2006, the number of meth busts nationwide has started climbing again. Some experts say the black market for cold pills contributed to that spike. Other factors are at play, too, such as meth trafficking by Mexican cartels and new methods for making small amounts of meth.

The AP reviewed DEA data spanning nearly a decade, from 2000 to 2009, and conducted interviews with a wide array of police and government officials.