Traces of asbestos have been found in crayons and children's toys, according to a report from EWG Action Fund.

The advocacy group said asbestos was present in four of 28 boxes of crayons. Furthermore, the analysis from a private laboratory hired by the group also tested toy crime-laboratory kits and found that two of 21 were positive for asbestos. A second private laboratory confirmed all the results.

EWG Action Fund also reported that the laboratory tests revealed higher asbestos concentrations in crime-scene kits compared with crayons. The crayons and toys evaluated carried packaging labels that indicated they were manufactured in China.

CNN gave away brand names to crayons that were positive for the carcinogenic substance. They include Disney Mickey Mouse Clubhouse and Amscan Crayons bought from Party City. On the other hand, two of the asbestos-positive crime-laboratory kits were sold at ToysRUs.com and Amazon.

Distributors, retailers and importers of the affected products have already been contacted for comment, the news outlet said.

There had already been cases of asbestos contamination in crayons and crime-laboratory toy kits in 2000 and 2007, according to report co-author Sonya Lunder.

She also described the discovery as a surprise because manufacturers of the products involved had previously promised that the problem would be dealt with.

Asbestos had been long banned in many EU nations and is also no longer commonly used in the U.S. With the latest report, health experts start to express their concern.

"Even if the absolute risk is relatively low, children are more vulnerable to toxic material and carcinogens," said Richard Lemern, former U.S. assistant surgeon general, according to CBS News.

Asbestos fibers are so tiny and cannot be seen by the naked eye. Accumulation of these fibers in the body can lead to breathing problems and ultimately, lung cancer.

"Just a couple of fibers can lodge in your lungs and be there forever," Lunder said, adding that there existed "very clear evidence" that the material could lead to the development of two types of cancer, and thousands of Americans have already died from exposure.

EWG Action Fund is now calling for a ban the use of asbestos in consumer products.