The U.S. Treasury Department's sanctions office was hacked by the Chinese government, the Washington Post reported on Wednesday, citing unnamed officials. The department earlier this week disclosed in a letter to lawmakers that Chinese state-sponsored hackers stole documents in what Treasury called a "major incident.

The US Treasury Department told lawmakers in a letter back in December that its documents and workstations were accessed by an external party in a security breach. It described the attack as "a major cybersecurity incident" and attributed it to a "China state-sponsored Advanced Persistent Threat actor.