China-based hackers breached the email accounts of dozens of organizations, including some United States government agencies, in an apparent espionage campaign aimed at obtaining sensitive information, Microsoft and the White House said late Tuesday, CNN reports.

The full scope of the hack is being investigated, but US officials and Microsoft have been quietly trying in recent weeks to assess the impact of the cyberattack, which targeted unclassified email systems.

The federal agency where the Chinese hackers were first identified was the State Department, a person familiar with the matter told CNN. The State Department subsequently reported the suspicious activity to Microsoft.

And the Commerce Department, which has imposed sanctions on Chinese telecommunications companies, has come under attack. Hackers accessed Commerce Secretary Gina Raimondo’s email account, a source familiar with the investigation told CNN.

Chinese hackers were found to be targeting a small number of federal agencies and only a small number of official email accounts in each agency in a cyber attack that targeted specific officials, multiple sources familiar with the investigation told CNN.

“Microsoft notified the Commerce Department about a breach in Microsoft’s Office 365 system, and the Department took immediate action to respond,” a department spokesman said.