West Ham has launched an investigation following fresh reports of crowd trouble at the London Stadium on Saturday and vowed to take a "zero tolerance policy" against any "mindless individuals" found guilty.
Several arrests were made as clashes broke out between rival supporters outside the stadium in the wake of the Hammers' 1-1 draw against Middlesbrough.
The violent scenes marked the third time this season there have been disturbances at the ground.
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West Ham's first Premier League home game at the venue, a match against Bournemouth, was marred by scuffles both inside and outside the ground, while last month's clash with Watford saw 10 people ejected from the stadium.