Hackers based in China have breached U.S. government email accounts, including two executive branch agencies, one of which was the State Department.

"We did two things immediately. One, we took immediate steps to secure our systems, and two, took immediate steps to notify Microsoft of the event," State Department Spokesman Matthew Miller said.

He wouldn't comment on who may have carried out the hack, but said anomalous activity was detected last month. He said steps were taken to secure the State Department system and an investigation is underway.

The 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 incident remains under investigation and we continuously monitor our networks and update our security procedures," Miller said.

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