United States Penitentiary Atwater was placed on modified operation on Friday while prison staff investigates a potential threat to staff members, according to a news release.
The prison will return to normal operations as soon as it can, according to the news release. Staffers did not describe the type of potential threat.
At no time is the public in danger during the investigation, according to the news release.
USP Atwater is a high-security level facility which houses about 1,106 male offenders.