A pack of crayons sold at Dollar Tree has tested positive for traces of asbestos, according to a consumer watchdog group.

The US Public Interest Research Group is advising Dollar Tree to recall the crayons and contact customers to let them know.

A Dollar Tree spokesperson said that the crayons had passed all of its legal and safety requirements but did not comment on whether the items would be recalled.

A consumer watchdog group is warning customers that some crayons sold at Dollar Tree have tested positive for traces of asbestos.

On Tuesday, US Public Interest Research Group released its annual report about the safety of school supplies. Dollar Tree's Playskool crayons, specifically the green-colored crayon sold in each $1 pack, were highlighted as testing positive for traces of tremoline, a kind of asbestos. It recommends that Dollar Tree recall the "asbestos-tainted crayons" and contact customers to warn them about the crayons.

Dollar Tree did not comment on whether it would be recalling these items, but told Business Insider that the crayons "passed all legal and safety requirements."

A company spokesperson told Business Insider:

"The safety of our customers and associates is our top priority. Our Company utilizes a very stringent and independent testing program to ensure our supplier products meet or exceed all safety and legal standards. We are aware of the report and have since re-verified that each of the listed products successfully passed inspection and testing."

In its investigation, US PIRG purchased children's school supplies across the country, from big-box stores, dollar stores, drug stores, online retailers, and arts-and-crafts stores. Samples were sent to an independent laboratory, the STAT Analysis Corporation in Chicago, and any that tested positive for potentially harmful chemicals were retested for further confirmation. The crayons that tested positive were purchased in a Dollar Tree in Chicago.

Asbestos is a known carcinogen that can lead to serious health conditions, including cancer in the lungs, larynx, and ovaries, as well as many cases of mesothelioma.

This is not the first time that asbestos has made its way into crayons. In 2000, asbestos was found as a binding agent in both Crayola and Rose Art crayons. At the time, the US Consumer Product Safety Commission said that the risk of children being exposed to these fibers through inhalation was extremely low. However, it asked manufacturers to voluntarily recall the crayons.

"We recommend that children not be exposed to asbestos. This level of asbestos is low. But because children are a vulnerable population, we think it is an unnecessary risk to expose children to a known carcinogen like asbestos,"US PIRG's Kara Cook-Schultz said in a statement emailed to Business Insider.

She added: "If parents want to keep their children from using crayons that contain asbestos, we recommend that they do not use the 36-count Playskool crayons sold by Dollar Tree."

Six other packs of crayons, including the Crayola brand and Rose Art, were also tested. The tests came out negative for any traces of asbestos.

"We have informed the CPSC about our recent Playskool results and asked the CPSC to do their own investigation. We have asked Playskool to do a voluntary recall and to reformulate their crayons, as other manufacturers have done in the past," Cook-Schultz said.