June 12 (UPI) -- A cyberattack has crippled distribution channels for one of the nation's top organic food distributors, leading to empty shelves at grocery stores nationwide.

Rhode-Island-based United Natural Foods Inc., a major supplier to Whole Foods, became aware of the attack on June 5th, a filing with the Securities and Exchange Commission said. UNFI said the breach affected its ability to fulfill customer orders.

"It's affecting operations in a very, very significant way," an employee at a Sacramento Whole Foods told NBC News. "Shelves don't even have products in some places. The shipments we receive are not what we need, or we did need it but it's too much of one product because UNFI can't communicate with stores to get proper orders."

A spokesperson for Whole Foods apologized and said the company is working to restock the shelves as quickly as it can. In a statement, UNFI acknowledged the ransomware attack.

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