Investigators bought 47 products from Walmart, Amazon, eBay, Sears Marketplace and Newegg. Of those products, 20 were fakes, the Government Accountability Office said in a new report released Tuesday.
The products include everything from makeup to phone chargers and athletic shoes.
The items were all sold by third-party sellers with average customer ratings above 90 percent and all were shipped from U.S. addresses.
The 47 items purchased were advertised as new, name-brand items.
>> Related: Forget the exercise, wine or a few beers a day is recipe for long life, new study says
According to the report, of 13 Urban Decay cosmetics purchased across the five sites, all were found to be counterfeit, as were six of nine Yeti Mugs. Out of 10 UL-certified phone chargers that are commonly used for iPhones, one was a fake, but all 15 pairs of Nike Air Jordan shoes were the real thing.
But more troubling is that federal authorities warn that counterfeit products can be dangerous, or even deadly, to consumers.
The report says an examination of 400 counterfeit iPhone adapters found that some “posed a risk of lethal electrocution.” Counterfeit travel mugs may have higher concentrations of lead than recommended and counterfeit cosmetics contain such substances as cyanide, arsenic, mercury, lead, urine and rat droppings.
Spokespeople for Amazon, eBay, Walmart, Newegg and Sears Marketplace told CBS News they have stringent procedures and that counterfeit products and sellers found to be peddling fake items are removed from their marketplaces.
The two main federal agencies in charge of stopping counterfeit products from entering the country are U.S. Customs and Border Protection and U.S. Immigration and Customs Enforcement.
>> Related: Birmingham, New York woo Delta headquarters amid NRA-tax break fight in Georgia
CBS News reported in 2016, CPB conducted 31,000 seizures of counterfeit items that would be worth $1.38 billion if the products were authentic.
Data from CPB showed that most of the seized products came from China and Hong Kong.