HARRISBURG — A federal civil rights investigation has concluded that a state prison in Western Pennsylvania kept inmates with serious mental illness in solitary confinement for months or even years at a time.

The U.S. Justice Department issued its findings on Friday.

The agency says the State Correctional Institution at Cresson in Cambria County violated the constitutional rights of inmates with mental illness and intellectual disabilities by keeping them in their cells 22 to 23 hours a day.

The state Department of Corrections plans to close Cresson, but the Justice Department says the misuse of solitary confinement could extend to prisons statewide. The Justice Departments says it will expand its probe to include all state lockups.