The American company United Natural Foods (UNFI) reported a cyberattack to the U.S. Securities and Exchange Commission (SEC) in a recent filing. UNFI stated that it detected unauthorized activity on its Information Technology (IT) systems on June 5 and has been investigating the incident while working to safely restore its systems.

According to the official filing, the organic food distributor had to shut down certain systems to contain the attack, which has affected customers’ orders. UNFI serves over 30,000 supermarkets and stores across the United States and Canada, including its main partner, Whole Foods.

The company said it is implementing alternative measures to minimize the impact of disruptions—but multiple clients are already experiencing significant consequences.

“The incident has caused, and is expected to continue to cause, temporary disruptions to the Company’s business operations,” states the document. “The Company is working actively to assess, mitigate, and remediate the incident with the assistance of third-party cybersecurity professionals and has notified law enforcement.”

According to NBC News, multiple stores have been facing shortages in the past few days, and customers have been facing empty shelves at Whole Foods in the past few days.

The specifics of the attack have not been disclosed, as it is an ongoing operation. However, some experts have linked the incident to the recent wave of cyberattacks targeting retailers in the UK—including the multinational retailer Marks & Spencer—and the United States, involving ransomware.

During a financial quarter meeting on June 10, UNFI’s CEO, Sandy Douglas, said they have been working with the FBI and other authorities to understand why and how their security systems have failed to improve their technology defenses.

“We just got penetrated, so we will be continuing to look at every aspect of our defense, every aspect of how our tools are working, and what may be necessary to bolster it going forward, because it’s clearly an area that requires a tremendous amount of focus from companies today,” said Douglas, as reported by USA Today.