Well-dressed racegoers were caught in a “large-scale” fight about a mile fron the famous racecourse on Friday.
Around 7.30pm police officers were called to the scene following reports of an escalating row between two groups of people.
A 16-year-old boy was arrested on suspicion of affray but has since been released under investigation.
Superintendent Dave Charnock of Merseyside Police said: “This kind of violent disorder in a public place will not be tolerated and we are currently examining CCTV and video footage and following a number of lines of inquiry to identify those responsible.
“A dispersal zone has been put in place to tackle anti-social behaviour and high-visibility patrols will be stepped up in the area over the weekend.
“This means that any groups of people gathering in the areas of Old Roan to Warbreck Moor can be moved on. I would ask anyone who witnessed the incident or has any footage to contact us.”
He added: “Despite this incident occurring away from the racecourse, the actions of individuals involved have tarnished what was an otherwise fantastic day for racegoers and we will continue to pursue those responsible and put them before the courts.