West Ham United have vowed to ban any supporter found to have attacked visiting journalists.
Eintracht Frankfurt defeated the Hammers 2-1 in their Europa League semi-final first leg at London Stadium on Thursday night.
German reporters, Tim Brockmeier and Philipp Hofmeister, said they were punched by the supporters.
In a statement, a West Ham spokesperson said: "The club is aware of the incident and will be working to identify the offender. In line with our zero-tolerance approach, anyone identified will have their details passed to the police.
"They will be given an indefinite ban and be unable to enter London Stadium and travel with the club. There is no place for this kind of behaviour."
Hofmeister says during the live broadcast: "If you constantly have the feeling that something could come from behind, a punch or something. My dreams of English football have been shattered."
After the game Hofmeister tweeted: "We are doing okay. Best wishes to all West Ham supporters who love football and respect their opponents."