West Ham players confronted AZ Alkmaar fans who appeared to attack an area in which friends and family were watching the teams’ Europa Conference League semi-final second leg.
Michail Antonio and Said Benrahma were among those to intervene in the clashes just moments after the Premier League team had reached the final.
BBC commentator Alistair Bruce-Ball, who was inside the stadium, said he saw punches being thrown by the AZ fans.
“These are awful scenes,” he said.
West Ham manager David Moyes said his players were “angry”.
“We’ll need to wait for the dust to settle to see what it is but the biggest problem is that is the area where the players have all their families in,” he said.
“That is where the problem came, and a lot of players were getting angry because they couldn’t get to see if they were OK.
“We’ll have to wait and ask the officials what really happened. I can only tell you that players were involved because that…