Romelu Lukaku applauded Manchester United fans after the win over Southampton
Manchester United have asked police for CCTV footage to help identify fans who sang a controversial song about striker Romelu Lukaku during Saturday's win at Southampton.
Lukaku, 24, asked fans to "move on" from the chant on Friday.
However, the song was heard in United's 1-0 Premier League victory at St Mary's Stadium.
"The club and the player have been clear in asking for an end to the chant," a United statement read.
"The club has worked with relevant bodies and supporters groups in trying to eradicate any offensive behaviour and will take further action against individuals if this continues."
United said they have a "zero-tolerance stance" on offensive chanting and behaviour.
Anti-discrimination group Kick It Out previously described the lyrics - about the size of the 24-year-old's penis - as "offensive and discriminatory".
Speaking after the match, manager Jose Mourinho said he did not understand any of the songs heard at football matches.
He added: "I don't understand what the fans sing. The only music I understand clearly is one of my opponents - not today but in other games - where they tell Mourinho to go to some place.
"The only thing I will say is the support was amazing from the first to the last minute."
Source: bbc.com