The U.S. Food and Drug Administration (FDA) has designated a voluntary recall of several potato chip products as a Class I recall, the agency’s highest risk classification, over concerns of possible salmonella contamination.

Utz Quality Foods originally announced the recall on May 5, affecting select varieties of Zapp’s and Dirty Brand potato chips. The company said it took action after a third-party supplier notified it that a seasoning blend containing dry milk powder may have been contaminated with Salmonella.

Although Utz said the affected seasoning batches tested negative for Salmonella before they were used in production, the company decided to recall the products as a precaution.

In an enforcement report released Wednesday, the FDA confirmed that all six affected products have been classified as a Class I recall. The agency reserves this designation for situations in which there is a reasonable probability that using or consuming the affected product could result in serious health consequences or death.

Utz emphasized that the recall was initiated “out of an abundance of caution” following the supplier’s notification, despite the company’s own testing showing no evidence of contamination in the seasoning batches.

The company voluntarily recalled nine varieties of Zapp’s and Dirty Brand chip flavors and bag sizes, which Utz said were sold at retail stores nationwide:

1.5-ounce Zapp’s Brand Bayou Blackened Ranch Potato Chips
2.5-ounce Zapp’s Brand Bayou Blackened Ranch Potato Chips
8-ounce Zapp’s Brand Bayou Blackened Ranch Potato Chips
2-ounce Dirty Brand Salt and Vinegar Potato Chips
1.5-ounce Zapp’s Brand Salt and Vinegar Potato Chips (60-count)
2-ounce Dirty Brand Maui Onion Potato Chip
2.5-ounce Zapp’s Brand Big Cheezy Potato Chip
8-ounce Zapp’s Brand Big Cheezy Potato Chip
2-ounce Dirty Brand Sour Cream and Onion Potato Chips

According to Utz, no other products produced by the food manufacturer are included in the recall.