An actor affiliated with the Chinese government recently hacked the U.S. Treasury Department in a “major incident,” officials announced on Monday.

In a letter obtained by FOX Business, the Treasury Department disclosed the incident to Senate Banking Committee leadership. Officials learned of the breach on Dec. 8.

The cybercriminal reportedly gained access to Treasury Department workstations and documents via a security key.

“Once Treasury was alerted by the service provider, we immediately contacted Cybersecurity and Infrastructure Security Agency (CISA) and have worked with law enforcement partners across the government to ascertain the impact of this incident,” the spokesperson said.

“The compromised BeyondTrust service has been taken offline and there is no evidence indicating the threat actor has continued access to Treasury systems or information.”

The news came as the state-affiliated Chinese hackers continue an espionage campaign against the U.S. government. Last week, the White House said that Chinese officials accessed Americans’ private texts and phone conversations through the targeting of a U.S. telecommunications company – the ninth telecom company to be affected by Chinese hacking.

Speaking to reporters, deputy national security adviser Anne Neuberger said that the government was planning further action in the coming weeks in response to the hacking campaign, but did not disclose specific details.

Neuberger said that the number of Americans impacted by the recent telecom attack is unknown because Chinese hackers are careful about covering their tracks. Many of the victims were located in Washington, D.C., and Virginia.

‘We believe it was the goal of identifying who those phones belong to and if they were government targets of interest for follow-on espionage and intelligence collection of communications, of texts and phone calls on those particular phones,” she explained.

Salt Typhoon, which is what U.S. officials call the Chinese government’s espionage unit, has been active for the past four years. It is unknown if the most recent Treasury incident involved Salt Typhoon or another CCP-affiliated actor.