A new analysis reveals Wednesday that over 20 popular children's cereals and snacks are contaminated with glyphosate—the main ingredient in the weedkiller Roundup.

The testing was commissioned by the Environmental Working Group (EWG)—the thirdround of such testing it's undertaken—and looked at popular General Mills-made products, including several Cheerios varieties and various kinds of Nature Valley granola bars.

The findings come as glyphosate, which the World Health Organization's International Agency for Research on Cancer declared a "probable carcinogen" in 2015, faces legal scrutiny as thousands of non-Hodgkin's lymphoma sufferers say that Bayer-Monsanto's Roundup caused their cancer. Three courts in California have so far sided with plaintiffs and ordered the agri-chemical giant to pay billions in damages.

"As these latest tests show, a box of Cheerios or other oat-based foods on store shelves today almost certainly comes with a dose of a cancer-causing weedkiller," said Olga Naidenko, Ph.D., vice president for science investigations at EWG.

According to EWG's new testing of 21 products, the highest concentrations of glyphosate were found in Honey Nut Cheerios Medley Crunch (833 parts per billion,) Cheerios Toasted Whole Grain Oat Cereal (729 ppb), and the maple brown sugar variety of Nature Valley Crunchy granola bars (566 ppb).

The advocacy group puts the health benchmark for children's daily glyphosate exposure at 160 ppb. That leaves only four of the products tested within the acceptable range: Honey Nut Cheerios (147 ppb); Nature Valley Fruit & Nut Chewy Trail Mix Granola Bars, Dark Chocolate & Nut (76 ppb); Nature Valley Sweet & Salty Nut granola bars, Cashew (158 ppb); and Nature Valley Soft-Baked Oatmeal Squares, Cinnamon Brown Sugar (124 ppb).

In light of the results, EWG is calling on consumers to "tell General Mills to get Monsanto's weedkiller of out their products."

"Does General Mills really want to keep using a chemical that independent scientists say causes cancer, made by a company that three juries have found guilty of covering up its health hazards?" asked Naidenko. "Or will they listen to the growing chorus of concerned consumers calling on General Mills and other companies to remove glyphosate from the cereals kids love to eat?"

The Trump administration maintains that glyphosate is safe for public health.