Sneaking a bite of the batter before baking cookies can make you ill, a new report by the Centers for Disease Control and Prevention warns. Unbaked cookie dough may contain pathogens such as E. coli or salmonella bacteria. Such raw-dough snacking was linked to an E. coli outbreak in 2009.

“What our report shows is that you shouldn’t eat cookie dough raw, no matter where it comes from,” said the report’s lead author, Dr. Karen Neil, a medical epidemiologist. “It’s supposed to be baked.”

The CDC investigation found E. coli in samples taken from manufacturing plants, which led to a recall of 3.6 million package of an unidentified brand of cookie dough.

The report suggests the pathogen-hosting culprit may be raw flour, which doesn’t go through the same processes as eggs, sugar, baking soda, and margarine. Flour and flour-based mixes have been known to contain low levels of salmonella bacteria.

The CDC’s findings were published in the journal Clinical Infectious Diseases.