Manchester City have confirmed a supporter is in a critical condition in hospital after an alleged assault following their Champions League match away to Schalke.
Members of club staff have not travelled back to Manchester after Wednesday's last-16 first leg in order to support the fan's family.
City asked for anyone who has information about the incident to get in touch with police.
"Manchester City are aware of an alleged assault after the match at the Veltins-Arena in Germany last night," said a club statement.
"The club are working with Greater Manchester Police and German Police to ascertain more information.
"Club staff have remained in Germany to support the family of an injured City fan who is currently in a critical condition in hospital."
Pep Guardiola's team won the match 3-2 thanks to strikes from Sergio Aguero, Leroy Sane and Raheem Sterling - the latter two goals coming after Nicolas Otamendi received a second-half red card.
