Police are questioning a man in connection with an alleged racist gesture made by a fan during Liverpool's FA Cup victory over rivals Manchester United.
Merseyside Police said the 59-year-old suspect, from the North Wales area, was held on Saturday evening hours after the game at Anfield.
Earlier, a television image capturing a Liverpool fan making an alleged racist gesture during the clash was distributed on social networking websites sparking a number of complaints to the force.
Officers later confirmed they were investigating the incident.
A force spokesman said: "Merseyside Police can confirm that a 59-year-old man from the North Wales area has been arrested following an alleged incident at the Liverpool versus Man U match.
"The man has been taken to a police station and will be questioned by officers. Merseyside Police would like to thank North Wales police and Liverpool Football Club for their assistance with this matter."
It was the first game between the rivals since the eight-match ban imposed on Liverpool striker Luis Suarez after the FA found him guilty of racially abusing United defender and captain Patrice Evra.
Before the match, in which Liverpool triumphed 2-1, the stadium announcer warned supporters that racist and homophobic behaviour would not be tolerated.
It is understood that home supporters found guilty of such offences inside the ground would be subject to life bans from the club.