WALLA WALLA, Wash. (AP) - Four units with a total of about 750 prisoners are locked down at the Washington State Penitentiary at Walla Walla.
The prison says the lockdown follows an assault Tuesday night in which one offender was injured. No prison staff members were hurt.
Guards found a sharpened weapon used in the assault, which is under investigation.
The Penitentiary houses about 2,000 offenders in four levels of security.