A small power plant in the United Kingdom was reportedly shut down for four days in July following a cyberattack allegedly carried out by hackers linked to Iran.

The incident occurred around the time U.S. officials warned that Iran-linked cyber actors were targeting water and other critical infrastructure.

The British government declined to identify the facility or confirm who was responsible, but said the incident posed no threat to the wider energy system.

Officials briefed energy companies on the incident and are updating cybersecurity regulations to strengthen protections for critical infrastructure, CNBC has reported.

The report comes amid growing concerns about cyberattacks linked to Iran, including recent U.S. charges against 17 Iranians accused of conducting a major cyber theft campaign.