The Whetstone Unit of the Arizona State Prison Complex in Tuscon was locked down on Sunday after a fight involving 400 inmates broke out at 9:45 a.m.
The brawl included an estimated 300 white and Mexican-American prisoners and 100 African American prisoners, according to Dylan Smith of the Tuscon Sentinel.
17 inmates were injured, the extent to which was not immediately available. Two staffers also suffered mild injuries. The minimum-security Whetstone unit houses a total of 1,250 prisoners. No prisoners from other units were involved in the fight.
Authorities did not know the cause of the fight or the cause of a similar large-scale brawl that took place between 200 prisoners in the Santa Rita unit of the same prison last September, which left 11 inmates and 2 prison guards injured.
Speculation that Sunday's brawl was a “race riot” stems from a previous U.S. Department of Justice investigation into racial profiling by Maricopa County Sheriff Joe Arpaio in 2012.
Pending an investigation, all visitation at the prison was suspeded for the day after the fight.