PORTAGE, Wis. (AP) — State officials say the maximum-security Columbia Correctional Institution remains locked down following another assault on a staff member.

The Department of Corrections says the lockdown, which restricts prisoners’ movement, began after the latest assault Friday. Corrections spokeswoman Clare Hendricks says there were also two additional and separate staff assaults at the Portage prision in the past weeks.

Hendricks says DOC is working with law enforcement to investigate the latest assault, but no other details about the incident are being released.

She says the prison will remain locked down until corrections officials believe it’s safe to lift the restrictions.