West Ham condemned the behaviour of “a small number of fans” after Fiorentina’s Cristiano Biraghi was hit by an object thrown from the stands at the Europa Conference League final.
Biraghi was left bloodied after cups and other items were thrown as he took a corner during the match in Prague.
West Ham said “these actions have no place in football”.
It followed trouble before the game, as 16 people were arrested after an incident at a bar.
Czech police said Italian fans attacked West Ham supporters in a bar, leaving three people injured.
West Ham said the fans’ actions inside the Fortuna Arena “do not in any way represent the values of our football club and the overwhelming majority of our supporters”.
The club added that fans had “behaved impeccably” in Prague and during their time in European competitions in the last two seasons, and that they would assist police in finding the culprits.
“In line with our zero-tolerance approach, anyone identified will have their details passed to the police and will be given an indefinite ban and therefore be unable to enter London Stadium and travel with the club,” a statement said.