Whole Foods has issued a warning to customers following a cyberattack on its main supplier.

The supplier, United Natural Foods (UNFI), was forced to shut down certain systems after detecting unauthorized activity on its internal networks in recent days.

As a result, Whole Foods has alerted employees about the potential for food shortages at its more than 500 locations across the US, according to an internal memo obtained by TechCrunch.

The Amazon-owned grocery store added that the cyberattack has impacted UNFI's 'ability to select and ship products from their warehouses,' and that this will 'impact our normal delivery schedules and product availability.'

Whole Foods spokesperson Nathan Cimbala said: 'We are working to restock our shelves as quickly as possible and apologize for any inconvenience this may have caused for customers.' 

Shoppers have shared images of their trips to the store, showing that many of the shelves are empty. 

Ed Clearly, a Florida native spending the summer in Pennsylvania, posted on X: 'Small sample size of how empty these store shelves were today. Truly remarkable.'

'[I] haven't seen a store like this since a hurricane was barreling towards Florida.'

UNFI said Wednesday that it is slowly restoring its systems, adding that it should increase 'capacity over the coming days.'

The supplier is the largest publicly traded wholesale distributor of 'healthier food options' in the US and Canada, according to its website. 

It operates 53 distribution centers and delivers goods to over 30,000 stores. 

In May 2024 the company announced an eight-year extension to serve as primary distributor for Amazon-owned Whole Foods.

The memo also provided staff a talking point when dealing with questions from customers, prompting them to only says that UNFI has been experiencing a 'nationwide technology system outage,' according to TechCrunch.

Julie Chang, a California local, was met with empty shelves during her visit to a Whole Foods in San Diego.

'At Whole Foods just now. Lotsa shelves empty I asked what's going on. One of the largest food distributors in the US got cyberattacked,' she posted on X.

'That's troubling the food supply can be disrupted this way.'

The same scene has also been reported in Illinois, Colorado and Florida.

One Whole Food shopper shared that their location 'hasn't had water, eggs, real or milk substitutes for days.'

The grocery store has been forced to display signs where shelves and cases are barren, which read: 'We are experiencing a temporary out of stock issue on some products.'

The company said the incident temporarily hurt its 'ability to fulfill and distribute customer orders.' 

'We apologize for the inconvenience and should have your favorite product back in stock soon.' 

A Whole Foods spokesperson told Reuters in an email on Monday that the company was 'working to restock our shelves as quickly as possible' and referred additional questions back to United Natural. 

UNFI, based in Rhode Island, said in a June 9 filing with the Securities and Exchange Commission that it “proactively” took some systems offline after becoming aware June 5 of unauthorized activity on certain networks.

The company said the incident temporarily hurt its "ability to fulfill and distribute customer orders.” It added that the incident "is expected to continue to cause temporary disruptions" to its operations.