H-E-B confirmed a quality issue with one of its egg suppliers left mold inside a small number of eggs sold at its stores.

Shoppers began reporting the problem on social media roughly two weeks ago, with most complaints coming from the Austin, Texas, area, according to Supermarket News. Several customers said they found mold on the inside of eggs sold at H-E-B.

The San Antonio-based grocer has not disclosed exactly how many eggs the mold affected. H-E-B said shoppers can return the eggs for a full refund.

One shopper discovered the mold after boiling brown eggs and cracking them open.

"I've never come across something like this with an egg before," the shopper wrote on Reddit. "So, I'm pretty shocked."

Another Reddit user posted more detail. That shopper cracked raw eggs, found mold, and included a picture showing the product's origin: H-E-B Cage Free Extra Large Brown Eggs, 30 count.

Reddit users speculated about the cause. "Lack of climate control practices when transported from farm to market, apparently," one poster suggested. Another poster said she found the same issue with eggs she had purchased.

H-E-B attributes the contamination to a single supplier's quality problem rather than an issue inside its own operations. The company has not said whether it has dropped the supplier or changed its sourcing.

For H-E-B, the episode is a reminder of how quickly supplier-level quality failures surface on social media and reach shoppers. The grocer's refund offer gives affected customers a remedy, but the number of moldy eggs reaching shelves remains undisclosed.