Update: After this piece aired, Amazon appeared to remove the toys featured in the story from its website.
Children's toys sold in the United States are subject to more than 100 tests and requirements to protect children from things like choking hazards or misleading age recommendations. But somedon't meet those standards, and could put kids at risk, CBS News national correspondent Errol Barnett reports.
CBS News purchased four products from third-party sellers through Amazon and had them tested at an accredited lab. According to the lab, all four samples failed safety tests.
A wooden jigsaw puzzle, marketed for kids as young as 1-year-old, included "small objects" that could be a choking hazard. Small toy trucks broke during testing, exposing "sharp points." Flashing LED rings "separated," exposing "the battery component." And a brand of magnetic putty, once advertised as "Amazon's Choice," contained a "hazardous magnet," stronger than what U.S. safety standards allow.
In a statement, Amazon wrote, "Safety is a top priority at Amazon. We require all products offered in our store to comply with applicable laws and regulations and have developed industry-leading tools to prevent unsafe or non-compliant products from being listed in our stores. When a concern arises, we move quickly to protect customers and work directly with sellers, brands, and government agencies."
Aaron Muderick, founder of "Crazy Aaron's Thinking Putty," said in a business dedicated to fun, dealing with apparent knockoffs sold online is anything but.
"It's sort of like a game of whack-a-mole," he said. "You hit one down and another one comes right back up."
Muderick said after he put his products up for sale on Amazon back in 2010, similar products quickly followed.
"Every single one of our unique products goes through a litany of safety testing," Muderick said. "When someone is knocking off a product, they're not spending that money. It is very difficult for customers to know, did this product actually pass these tests?"
His biggest concern right now is cheaper versions of his magnetic putty that use magnets that don't meet U.S. safety standards.
"The magnet needs to be a certain size that is extraordinarily unlikely that it could be swallowed," he said. "And also limitations in how strong a magnet can be."
Safety experts use a tube to check if pieces are small enough to create a choking hazard. While Muderick's magnets are too big to fit inside, the magnet from a similar product does. The other concern is the magnet's strength.
"Small magnets — if they're swallowed — they can really just cause a lot of problems in a child's digestive system," said Rebecca Mond with The Toy Association, a trade group representing U.S. businesses that design, produce, license and deliver toys.
A 4-year-old Wisconsin boy reportedly had to have part of his intestines removed after swallowing small magnets from a different knockoff toy.
"Our children should not be the testing grounds for the toys," Mond said.
Parents shopping online should look for reputable sellers they know, The Toy Association said.
"If a deal seems too good to be true, it probably is," Mond said. "Dig into the product listing a little bit deeper … Look at the reviews, and look at the product description for typos, grammatical errors."
But Muderick said online retailers must do more to keep kids safe.
"I think we're doing everything that we can do from our perspective but as long as these products continue to just ship in and this game of whack-a-mole sellers coming and going goes on … these products will remain on the market," he said.
CBS News tried contacting the four companies who listed the toys we tested, but only heard back from the company who sold the toy trucks. It told us its products meet "safety standards" and passed U.S. safety tests from a lab in China, but it did not test for all of the defects found by our lab.
An Amazon spokesperson said it is investigating the products in question.