Liverpool have condemned a "racist" banner depicting Divock Origi that was displayed by fans before Wednesday's Champions League win in Genk.
Travelling fans unfurled a graphic banner depicting the Belgium striker's head on a naked body, alongside the Champions League trophy.
The club said it "acted swiftly to have the banner removed" and said the image "perpetuated a racist stereotype".
"This is completely unacceptable," a club statement said.
"Liverpool Football Club condemns the offensive banner displayed in our section of the ground, prior to kick-off.
"We acted swiftly to have the banner removed and we are now working with the local authorities and stadium team in Genk to identify those responsible.
"Any subsequent action will be taken in keeping with our sanctions process."
On Thursday, Merseyside Police said Belgian police had launched an investigation into the banner.
A statement said: "We can confirm Merseyside Police officers, assisting local police, removed a banner in the Liverpool supporters' section.
"We worked with Liverpool FC and the local authorities to identify the person responsible, and the local police in Belgium are now conducting an investigation."
Origi, 24, spent nine years at Genk in the club's youth set-up before joining Lille in 2010.
He came on off the bench in the fixture at the Luminus Arena, where Jurgen Klopp's side won 4-1 to secure a second victory of the Champions League group stage.
Fans group Spirit of Shankly said: "The club took swift action in the removal of the offensive banner that perpetuates racial stereotyping.
"Football isn't separate from society, it is part of it and we all have a responsibility in ensuring people understand there is no room for racism.
"Simply banning people is not the answer. Education and reaffirming there is no place for discrimination in society has to form part of the solution."
If Uefa deems the banner to have been racist and charges Liverpool, the club could face a partial stadium closure at Anfield.
Levski Sofia were ordered to close 3,000 seats at their stadium after their fans displayed a racist banner in a Europa League match earlier this season.