The United States is warning of an “ongoing cyber threat” to industrial refrigeration systems, saying in a statement issued on Thursday that every organization that depends on cold storage should assume it could fall into the hackers’ crosshairs.

The statement, which follows a spate of hacks against commercial freezers in the United States and Europe, said that unidentified “malicious cyber actors” were targeting vulnerabilities in internet-accessible electronic temperature and commercial refrigeration controllers in retail grocery and cold storage facilities.

Although short on detail about the hackers involved, the statement suggested that the threat to commercial cold storage was ongoing.

“If successfully exploited, the actors could change the temperature and possibly cause physical impacts such as fire hazards, loss of inventory and changes to the service life of the system,” said the statement, which was jointly issued by the FBI, the Cybersecurity and Infrastructure Security Agency and the departments of health, transport and agriculture.

“Every organization that depends on refrigeration and monitoring systems should assume it could be a target,” said Chris Butera, CISA’s acting executive assistant director for cybersecurity.

FBI Cyber Branch Operations Director Brett Leatherman said that the government was “seeing these systems targeted across critical infrastructure sectors globally.”

The government urged operators of industrial refrigeration control systems to pull their devices off the public internet, isolate them from their corporate networks and promptly apply software updates.

At least three waves of hacks have hit commercial fridges and freezers in the past few months. Pentagon investigators are treating a series of mysterious malfunctions that hit grocery store refrigeration units on US military bases in August as a cyberattack, Reuters first reported last week. A sweeping hack of French freezers last month dealt tens of millions of euros’ worth of damage, while a second wave of hacking affected more than 100 stores across Europe on Monday.

The hacks have raised concerns over the ability of hackers to remotely tamper with refrigerators and other critical devices.

(Reporting by Raphael Satter in Washington; Editing by Chizu Nomiyama and Matthew Lewis)