Reports say hackers based in China breached U.S. government email accounts.
CNN reports hackers breached two executive branch agencies, including the State Department.
State Department Spokesman Matthew Miller would not comment on who may have carried out the hack, but said "anomalous activity" was detected last month.
He said steps were taken to secure State Department systems and an investigation is underway.
Hackers also reportedly targeted an agency on Capitol Hill but it's not clear if they were successful.
The hacking effort began in mid-May.
The Washington Post says one of the hacks targeted the Commerce Secretary Gina Raimondo emails.
The report says it was because of increased tarriffs on China.
Officially neither Microsoft or US officials are saying which agencies or departments were targeted.
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