Before you sprinkle some nuts onto your oatmeal or yogurt, you might want to give that bag a closer look: A bunch of walnuts have just been recalled, according to the FDA —and they may be behind an active E. coli outbreak that’s already sickened a dozen people, the CDC reports.

The FDA and CDC are investigating an E. coli outbreak linked to organic walnuts distributed in at least 19 states.

Organic walnuts from a California grower that were distributed to health food and co-op stores in 19 states have been linked to serious cases of E. coli illness, federal officials reported Tuesday.