(CNN) — An environmental advocacy group says several popular breakfast foods have round-up weed killer in them.

Cheerios and Nature Valley products are among the foods in the environmental working group’s report cited as containing trace amounts of Glyphosate. Some experts believe the controversial herbicide causes cancer.

Last month, a California jury awarded Monsanto to pay a couple more than $2 billion for their cancers after long-term exposure to the product.

General Mills, which makes Cheerios, admits pesticide residue can make its way into its products, but says the levels are much lower than what the federal government allows.

Researchers and agencies around the world are unsure whether Glyphosate causes cancer.