The U.S. Food and Drug Administration, which is quietly starting to test certain foods for residues of a weed killing chemical linked to cancer, has found the residues in a variety of oat products, including plain and flavored oat cereals for babies.

Data compiled by an FDA chemist and presented to other chemists at a meeting in Florida showed residues of the pesticide known as glyphosate in several types of infant oat cereal, including banana strawberry- and banana-flavored varieties. Glyphosate was also detected in “cinnamon spice” instant oatmeal; “maple brown sugar” instant oatmeal and “peach and cream” instant oatmeal products, as well as others. In the sample results shared, the levels ranged from nothing detected in several different organic oat products to 1.67 parts per million, according to the presentation.

Glyphosate, which is the key ingredient in Monsanto Co.’s Roundup herbicide, is the most widely used weed killer in the world, and concerns about glyphosate residues in food spiked after the World Health Organization in 2015 said a team of international cancer experts determined glyphosate is a probable human carcinogen. Other scientists have raised concerns about how heavy use of glyphosate is impacting human health and the environment.

The EPA maintains that the chemical is “not likely” to cause cancer, and has established tolerance levels for glyphosate residues in oats and many other foods. The levels found by the FDA in oats fall within those allowed tolerances, which for oats is set by the EPA at 30 ppm. The United States typically allows far more glyphosate residue in food than other countries allow. In the European Union, the tolerance for glyphosate in oats is 20 ppm.

Monsanto, which derives close to a third of its $15 billion in annual revenues from glyphosate-based products, has helped guide the EPA in setting tolerance levels for glyphosate in food, and in 2013 requested and received higher tolerances for many foods. The company has developed genetically engineered crops designed to be sprayed directly with glyphosate. Corn, soybeans, canola and sugar beets are all genetically engineered to withstand being sprayed with glyphosate.

Oats are not genetically engineered. But Monsanto has encouraged farmers to spray oats and other non-genetically modified crops with its glyphosate-based Roundup herbicides shortly before harvest. The practice can help dry down and even out the maturity of the crop. “A preharvest weed control application is an excellent management strategy to not only control perennial weeds, but to facilitate harvest management and get a head start on next year’s crop,” according to a Monsanto “pre-harvest staging guide.”

In Canada, which is among the world’s largest oat producers and is a major supplier of oats to the United States, the Monsanto marketing materials tout the benefits of glyphosate on oat fields: “Pre-harvest application of Roundup WeatherMAX and Roundup Transorb HC are registered for application on all oat varieties – including milling oats destined for human consumption.” Glyphosate is also used by U.S. oat farmers. The EPA estimates that about 100,000 pounds of glyphosate are used annually in production of U.S. oats.