Fifteen of 17 inmates injured in a fight at a Tucson prison have been released from hospitals and returned to prison.

Arizona corrections officials are investigating the cause of the fight that broke out among 400 inmates Sunday morning in a minimum-security unit of the Arizona State Prison Complex in Tucson.

Eighty of the inmates involved in the fight were moved to other institutions, said Bill Lamoreaux, an Arizona Department of Corrections spokesman.

Two prison employees suffered minor injuries.

Details haven't been released on the injuries suffered by the 17 inmates who were hospitalized.

The Whetstone unit of the prison where the fight broke out remained on lockdown Monday, while seven other sections of the prison are no longer locked down and have resumed regular operations.