Neither the agency nor Costco responded to NPR's messages for comment ... The FDA also placed the Class I designation on a recall of cucumbers due to possible salmonella contamination that, as with the eggs, was also announced in late November.

In November, Costco recalled nearly 260,000 eggs sold under the Kirkland Signature brand in 25 stores nationwide. The eggs landed on shelves in Alabama, North Carolina, Georgia, South Carolina and Tennessee starting Nov. 22, according to the company.

A major Costco egg recall due to possible salmonella was recently upgraded to a higher level by the Federal Drug Administration, NBC News reported, with officials saying those who consume the products could suffer "serious adverse health consequences or death.