WASHINGTON (AP) — Twenty people in the United States and abroad were arrested on charges they ran Internet pharmacies that illegally shipped narcotics, steroids and amphetamines to teenagers and other buyers around the world, federal authorities said Wednesday.

The arrests were the result of a yearlong investigation by six federal agencies of online pharmacies that operate in the shadows of the Internet, with no fixed address and no way to track their location, Drug Enforcement Administrator Karen Tandy said.

"The Internet has become an open medicine cabinet," Tandy said. "Strangers are peddling drugs in your home and you don't even know it."

But with the arrests, she added: "We've logged off some of the worst e-traffickers out there."