Over two dozen government agencies in Western Europe and the United States were hacked by a China-based espionage group, according to Microsoft and U.S. national security officials.

The hackers accessed Microsoft-powered email accounts at the agencies as part of a continued effort by China-based actors to spy on and steal sensitive government and corporate data. The hacking group, code-named Storm-0558 by Microsoft, also compromised personal accounts “associated” with the agencies, likely employees of the agencies.

The compromise was “mitigated” by Microsoft cybersecurity teams after it was first reported to the company in mid-June 2023, Microsoft said in a pair of blog posts about the incidents. The hackers had been inside government systems since at least May, the company said.

U.S. government officials identified the potential intrusion to Microsoft. The National Security Council didn’t identify which agencies had been impacted, although a bulletin from the FBI and the Cybersecurity and Infrastructure Security Agency said that the first report was made by a single executive-branch agency.

“Last month, U.S. government safeguards identified an intrusion in Microsoft’s cloud security, which affected unclassified systems. Officials immediately contacted Microsoft to find the source and vulnerability in their cloud service,” National Security Council spokesperson Adam Hodge said in a statement to the Wall Street Journal. “We continue to hold the procurement providers of the U.S. government to a high security threshold.”