The U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) has confirmed that it is responding to a cybersecurity incident that senior Justice Department officials have designated a “major incident” under federal guidelines. The disclosure came after the Qilin ransomware group publicly claimed to have targeted the agency.

ATF said the affected system operates separately from its main enterprise network and that there is currently no indication that the incident affected the agency’s broader network, eForms platform, or other ATF systems. The agency disconnected the affected environment and launched incident-response and forensic investigations in coordination with the Department of Justice.

While Qilin has claimed responsibility, ATF has not publicly attributed the incident to the ransomware group. Authorities are continuing their investigation, and the full scope of any potentially compromised information remains under assessment. ATF said the incident has not affected its ability to carry out its mission.