An underground website called Silk Road is selling synthetic drugs, thwarting authorities’ attempts to stop the illegal trafficking of these substances. According to the Star Tribune, the site and others like it continue to make these drugs easy to obtain even as a growing number of states are banning them.

The newspaper examined 86 drug websites, and found 64 appear to have been created in the past two years. The number of unique visitors to the sites jumped from 122,090 in June 2009 to 404,469 in June 2011.

“Bath salts” are a popular type of synthetic drug sold on these websites. Last week, the Drug Enforcement Administration (DEA) announced it is temporarily banning three synthetic stimulants that are sold as bath salts. The ban makes it illegal to possess and sell these chemicals or the products that contain them. The DEA said the action is necessary to protect the public from the imminent hazard posed by these dangerous chemicals.

The article notes that two months after Minnesota started enforcing a law banning bath salts and other synthetic drugs, they are still easily purchased from online sites.

DEA spokesman Will Taylor told the newspaper the task of trying to shut down these websites can be overwhelming. He said when the agency has been able to close down one of the sites, operators were quickly able to start another one.

The Silk Road site connects buyers and sellers, and hides buyers’ identities. The site does not use credit cards, instead relying on “Bitcoins,” an untraceable digital currency that is available through online currency exchange services. The website tells sellers to make shipments using vacuum-sealed bags so that drug-sniffing dogs will not detect the packages.

In June, two U.S. senators called on the federal government to shut down Silk Road, named after the ancient Asian trade route.