As back-to-school shopping ramps up, one advocacy group is calling for a popular brand of crayons to be recalled.

The U.S. Public Interest Research Group Education Fund said it found asbestos in Playskool Crayons that it tested from Dollar Tree.

The advocacy group released its 'Safer school supplies' shopping guide on Tuesday after testing a variety of popular school supplies for toxic chemicals.

According to the report, six crayon brands from different providers were each tested for asbestos, but only the Playskool Crayons 36-count product bought at a Dollar Tree store tested positive.

Lab results showed Crayola Crayons, Up & Up crayons classic, Cra-Z-Art crayons, Disney Junior Mickey and the Roadster Racers and Roseart crayons did not contain any asbestos.

The report recommended that Dollar Tree and Playskool recall the products and remove them from stores.

A spokesperson for Playskool's parent company, Hasbro, told The Washington Post it is conducting a "thorough investigation" into the report's claims and the crayon's manufacturer said it's also reviewing lab tests.

Meanwhile, Dollar Tree executives said its independent tests showed the crayons don't contain asbestos, according to The Washington Post.

U.S. PIRG is the same group that annually publishes a "Trouble in Toyland" survey highlighting potentially hazardous toys around the holidays.