Federal and state authorities are investigating at least 10 eBay auctions, some Oregon-based, found last week that offered thousands of pills containing pseudoephedrine, the critical ingredient in methamphetamine.
Quantities offered far exceeded new state laws on sales of the chemical.
Three auctions continued to take bids Friday. Three others apparently were shut down either by their owners or by eBay.
Ken Magee, assistant special agent in charge of the Drug Enforcement Administration in Oregon, said the auctions "piqued our interest tremendously."
With Oregon and other states passing laws restricting the sale of pseudoephedrine in recent months, buyers and sellers are finding new ways to obtain it.
"Crooks are becoming more savvy," said Garrison Courtney, a spokesman for the Drug Enforcement Administration in Washington, D.C. "They're realizing, 'Hey, here's a way to go through a keyboard anonymously, make cash and disappear.' " For at least six months, the DEA has worked with eBay and other online retailers to stop illicit sales of pseudoephedrine, Courtney said.