Chinese government hackers targeted the U.S. Treasury’s highly sensitive sanctions office during a December cyberattack, according to reports.

According to The Washington Post, the state-sponsored hackers targeted the Office of Foreign Assets Control (OFAC), a government department that imposes economic and trade sanctions against countries and individuals, to potentially access information on Chinese organizations that the U.S. government may be considering designating for financial sanctions.

The China-backed hacking group, which compromised the U.S. Treasury in December to access employee workstations and unclassified documents, also breached the Treasury Department’s Office of Financial Research and the Office of the Treasury Secretary, according to the report.

The cyberattack, described as a “major cybersecurity incident” by the Treasury, was discovered on December 8 when BeyondTrust, a third-party software provider of identity management tools, alerted the agency to a cybersecurity incident. 

The U.S. Treasury did not immediately respond to TechCrunch’s questions.