A cyberattack on an organic food distributor to blame for lightly stocked or empty shelves at grocery stores.

United Natural Foods, a Rhode Island-based supplier to Whole Foods and other retailers, said hackers have disrupted its operations. The country's largest organic food distributor revealed earlier this week in a filing with the Securities and Exchange Commission that it became aware of the attack on June 5.

The company said it took certain parts of its systems offline in recent days, which has hampered its ability to fulfill and distribute customer orders.

A spokesperson for United Natural Foods declined to share specifics about the cyberattack with NBC News , saying it was an "ongoing operation." The spokesperson said it wasn't clear when distribution would return to normal,

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