The United States Marshals Service says it was hit with a “major” security breach over a week ago, compromising systems that contained sensitive information.

U.S. Marshals Service spokesperson Drew Wade said in a statement to The Hill on Monday evening that the agency discovered the “ransomware and data exfiltration event” on Feb. 17, adding that it affected a “stand-alone” system. He said that after the discovery, the Marshals Service “disconnected” the system and the Justice Department initiated a forensic investigation.

“The affected system contains law enforcement sensitive information, including returns from legal process, administrative information, and personally identifiable information pertaining to subjects of USMS investigations, third parties, and certain USMS employees,” Wade said of the breach, which was first reported by NBC News.

A senior law enforcement official told NBC News that the hack did not affect the Witness Security Program, and that no one in the program is at risk due to it. The official added that the breach affected law enforcement sensitive information about the subjects of the agency’s investigations.

Wade said that the Marshals Service on Feb. 22 briefed senior Justice Department officials, who determined that the breach was a “major incident.” He added the Justice Department’s “remediation efforts and criminal and forensic investigations are ongoing” in relation to the incident.

“We are working swiftly and effectively to mitigate any potential risks as a result of the incident,” he said.

Data hacks have increasingly plagued federal and state governments, in addition to corporations and individuals, in recent years.