The FDA has upgraded a recall of Lay’s Potato Chips to the highest level possible, meaning consuming the chips will cause adverse health consequences. In December, Texas-based food manufacturer Frito Lay recalled a limited number of Lay’s Classic 13oz because the product could contain undeclared milk ingredients.

Lay’s voluntary recall from December has been increased to the U.S. Food and Drug Administration’s highest risk level classification. On Dec. 13, Frito-Lay recalled more than 6,000 bags of 13 oz. Lay’s Classic Potato Chips due to “undeclared milk.” The affected chips were sold in Oregon and Washington.