A number of seats were broken by Newcastle fans attending last night's Under-23s derby against Sunderland.
About 300 Magpies supporters were at the game, and the club has hit out at the action of a minority of those.
They say they will work with the police to identify those responsible.
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A statement from Newcastle United said: "Newcastle United is aware of the unacceptable behaviour of a number of its supporters who attended last night’s Under-23s match against Sunderland AFC at the Stadium of Light.
"The club is very disappointed to hear of the actions of a small group of individuals and will do everything it can to help the police identify those responsible and hold them to account."
Several seats were broken at the Premier League International Cup quarter-final, which Newcastle went on to win on penalties.