Some vinyl baby bibs made in China contain lead levels well above US safety limits for lead in paint, a California environmental group said.
The bibs were sold at Toys "R" Us, the US' second-largest toy seller.
A bib with Winnie the Pooh characters and store-brand bibs sold under the Koala Baby and Especially for Baby labels all tested positive for lead in concentrations three to four times what the US Environmental Protection Agency allows in paint, according to the Center for Environmental Health.
The group bought the four bibs at San Francisco Bay-area Toys "R" Us and Babies "R" Stores and contracted with a private lab that specializes in product safety to perform the tests.
"There's plenty of ways to make bibs without lead," Caroline Cox, the center's research director, said on Wednesday. "I don't think we should be exposing children to this toxic metal unnecessarily."
Lead most commonly occurs in vinyl products as a stabilizer or a pigment. It can also occur unintentionally when recycled vinyl used for other purposes becomes part of a new product.
Studies have repeatedly shown that childhood exposure to lead can cause learning problems, reduced intelligence, hyperactivity and attention deficit disorder.
Average US lead levels in the blood have dropped sharply in recent decades since the metal was restricted in paint and gasoline.
The Center for Environmental Health said it had notified Toys "R" Us that it intended to sue if the retailer failed to take the bibs off store shelves in California, a state with especially strict rules on lead exposure.
A Toys "R" Us spokeswoman said tests performed in May by a lab contracted by the company found the bibs met not just federal standards but California's more stringent limits on lead content.
However, more bibs were being pulled from the shelves on Wednesday for testing, spokeswoman Kathleen Waugh said.
Consumer anxiety over Chinese goods has risen in recent months with the discovery of contaminated pet food, toothpaste, seafood and toys made there.
Worries intensified on Tuesday after Mattel Inc recalled millions of toys made in China because of lead paint -- the company's second such recall in two weeks.
Both the bibs sold by Wal-Mart and Toys "R" Us were manufactured in China for Louisiana-based Hamco Baby Products.
China's problems with lead in consumer products go far beyond tainted toys.
From playthings to paint to gasoline, Chinese companies use lead in a wide range of products and experts say China's children are suffering the health consequences.
Beijing has prohibited leaded gasoline in recent years and has tightened standards for other goods.
But enforcement is spotty, and lead remains so common that researchers say up to one-fifth of Chinese children tested had unsafe levels in their blood.
"The central government many times has regulations in place, but given China's size, a lot of things don't get implemented at the local level," said Jamie Choi, a Beijing-based campaigner for the environmental group Greenpeace.
An official of trade group, the China National Light Industry Council, said that responsibility for meeting foreign standards should not lie with Chinese manufacturers.
"The quality of Chinese-made toys with American brands should be the responsibility of the American brand owner, not the Chinese manufacturer," said Zhang Yanfen, secretary of the council's panel on toy standards.