The U.S. Food and Drug Administration (FDA) announced Thursday it has shut down 1,677 illegal online pharmacies, CNN reports. The websites sold counterfeit or substandard medications, or sold drugs without appropriate safeguards.

Additional websites received warnings, the article notes. More than $41 million worth of illegal medicines were seized, and 58 people were arrested. Some of the sites had names that were similar to legitimate pharmacy sites. For instance, the FDA closed Walgreens-Store.com. It was not associated with the pharmacy chain Walgreens, which runs Walgreens.com.

The United States government worked with more than 100 countries to shut down the online pharmacies. Many of them advertised drugs such as Viagra, Levitra and Celebrex.

“These products can have none of the active ingredient that people need for the treatment of their disease,” said FDA Commissioner Margaret Hamburg. “They can have too much or too little (of the ingredient); they can have toxic ingredients, and they can prevent patients from getting the actual medications that they badly need to treat their disease.”

Carmen Catizone, Executive Director of the National Association of Boards of Pharmacy, told CNN most of the illegal online pharmacies are based overseas, and present themselves as Canadian. “The fact of the matter is very few, if any, of these sites are actually based in Canada or (are) Canadian,” Catizone said. “In fact, they are located in China, India, Pakistan, around the world.” The group has created a list of online pharmacies it has accredited.

“Illegal online pharmacies put American consumers’ health at risk by selling potentially dangerous products. This is an ongoing battle in the United States and abroad, and the FDA will continue its criminal law enforcement and regulatory efforts,” John Roth, Director of the FDA’s Office of Criminal Investigations, said in a news release.