Seventeen people were arrested amid "pockets of disorder" at a Championship football match, police have said.
Fans attending Middlesbrough's home game against Derby County were told to behave amid fears of tension over a recently resolved court dispute.
Cleveland Police said the "vast majority" did so but a "minority were intent on spoiling the day".
Offences included assaulting emergency workers, failing to disperse and possessing a flare.
The game had looked set to be played against a hostile backdrop until former Rams owner Mel Morris reached an accord with Boro owner Steve Gibson over the latter's compensation claim on Friday.