Hernandez "was involved in an altercation with another inmate" at the Bristol County House of Correction and Jail, said Bernie Sullivan, a spokesman for the Bristol County sheriff's office.
"Neither [man] was seriously injured," he added.
It wasn't clear if Hernandez, 24, would face criminal charges for the alleged fight, the Boston Globe reported Wednesday.
Hernandez has been held without bail at the jail since his arrest at his North Attleboro, Mass., home in late June. He is accused of killing Odin Lloyd of Franklin, Mass., on June 17. Lloyd was dating the sister of Hernandez's fiancee.