US Treasury Secretary Janet Yellen’s computer was infiltrated and unclassified files were accessed as part of a broader breach of the agency by Chinese state-sponsored hackers, according to two people familiar with the matter.

State-sponsored Chinese hackers breached U.S. Treasury Secretary Janet Yellen’s computer, accessing thousands of unclassified documents in December, anonymous sources told Bloomberg on Thursday. The hackers also infiltrated computers belonging to two of Yellen’s lieutenants,

The US Treasury Department announced in a letter back in December that it had been the victim of a security breach, attributing it to a “China state-sponsored Advanced Persistent Threat actor.” Now we know more about the extent of the hack,