Liverpool condemned a "highly offensive" banner of striker Divock Origi seen in the away end ahead of their Champions League game at KRC Genk on Wednesday.
Origi, 24, began his career with the Belgian side. His head was photoshopped onto the viral meme known as "WhatsApp Guy," which plays on a racial stereotype.
The poster was briefly hanging from the second tier of the Liverpool end at the Luminus Arena. Officials removed it as soon as it was flagged, before kickoff.
"The banner is highly offensive and inappropriate," a spokesperson for the European champions said.
"We condemn its use at the game tonight and sought to have it removed as soon as we became aware.
"We will look to identify those responsible for bringing it into the stadium and act accordingly."
A statement from the Merseyside police read: "We can confirm Merseyside Police officers assisting local police at the Genk v Liverpool fixture on Wednesday night (Oct 23) 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."