A series of refrigeration failures at U.S. military facilities and grocery stores across Europe has raised concerns about possible cyberattacks affecting supply chains.

The disruptions began drawing attention after refrigeration systems failed at military commissaries in the United States during the summer, spoiling food and temporarily limiting supplies. On Aug. 26, freezers at a market at Fort Huachuca, an Army base in Arizona, reportedly switched into defrost mode, causing all the food inside them to spoil.

That same day, Naval Station Newport in Rhode Island reported issues with its commissary refrigeration system. Army officials are investigating whether those incidents, along with other malfunctions at U.S. military facilities in August, were connected to a broader cyberattack.

The issue expanded to Europe last month, when freezers at hundreds of grocery stores in France malfunctioned in an incident officials described as a cyberattack. On Monday, retailers in at least seven additional European countries reported problems with refrigeration units.

The cause of the latest disruptions has not been established. However, experts said the incidents showed characteristics associated with cyberattacks. The U.S. Army said Monday that its cyber investigators were examining the matter.

The Pentagon also acknowledged speculation about a potential cyber incident and said its inspector general’s office was investigating.

Sources: The New York Times Technology.