Bristol County Sheriff Thomas Hodgson told the network that Hernandez got into an altercation with another inmate at the Bristol County House of Corrections on Tuesday. He declined to go into the specifics of the incident, but said jail staff are interviewing witnesses and reviewing surveillance footage as part of an internal investigation.
A spokesman for the Bristol County sheriff's office said neither man was seriously injured.
Hodgson said that the high-profile former tight end is was being held in a segregated area of the prison, distanced from the general population.
Hernandez's lawyers have not responded to press inquiries.
Hernandez is awaiting trail on murder and gun possession charges. He is charged with the slaying of Odin Lloyd, a former acquaintance who was found shot to death in an industrial park not far from Hernandez's North Attleborough, Mass. home.