"This is the first time I heard this -- I don't know how to pronounce -- this meta-meta something," said Hajira Ahmed, whose husband is in jail pending charges that he sold cold medicine and antifreeze at their convenience store on a winding road near the Tennessee border.

But David Nahmias, the United States attorney for the Northern District of Georgia, said the evidence showed that the clerks knew that the informants posing as customers planned to make drugs. Federal law makes it illegal to sell products knowing, or with reason to believe, that they will be used to produce drugs. In these cases, lawyers say, defendants face up to 20 years in prison and $250,000 in fines.

In one instance, Mr. Nahmias said, a store owner in Whitfield County pulled out a business card from a Georgia Bureau of Investigation agent and told the informant that he was supposed to contact the agent if someone requested large amounts of the materials. When the informant asked if he would call, Mr. Nahmias said, the owner replied, "No, you are my customer."

"It's not that they should have known," Mr. Nahmias said. "In virtually or maybe all of the cases, they did know."

Like many prosecutors, Mr. Nahmias describes methamphetamine, a highly potent drug that can be injected, ingested or inhaled, as the biggest drug problem in his district. While only about a third of the meth here is made in small labs -- the majority of the drug used in this country comes from so-called superlabs in Mexico -- those small labs can be highly explosive, posing a danger to children, the environment and the police departments that are forced to clean them up. Their sources, he said, are local convenience stores.

"While those people may not think they're causing any harm, the harm they cause is tremendous," Mr. Nahmias said. "We really wanted to send the message that if you get into that line of business, selling products that you know are going to be used to make meth, you're going to go to prison."

Operation Meth Merchant started, Mr. Nahmias said, with complaints from local sheriffs that certain stores were catering to the labs. Prosecutors paid confidential informants -- some former convicts, others offered the promise of lighter punishment for pending charges -- to buy products in stores in six counties beginning in early 2004, and drop hints that they were making drugs.