An altercation involving Crystal Palace boss Patrick Vieira on the Goodison Park pitch is being investigated by Merseyside police.
The incident took place in the aftermath of Everton's 3-2 comeback win over Palace in the Premier League on Thursday.
Widely circulated social media footage appeared to show Vieira kicking out at a supporter after being goaded, as Everton fans flooded onto the playing surface after Frank Lampard's team secured their top-flight status.
While Vieira refused to comment on the incident at his post-match news conference, the police have now announced an investigation, while reports suggest the Football Association has launched its own probe.
"Merseyside Police is investigating an altercation on the pitch at Goodison Park following the Everton v Crystal Palace match," read a statement released on Friday.
"We are working with Everton FC to gather all available CCTV footage and are speaking to witnesses. No formal complaint has been received and enquiries into the incident are ongoing."
Meanwhile, a separate statement released by the force confirmed three men had been arrested for entering – or attempting to enter – Goodison Park with pyrotechnics on Thursday, while another was arrested for a breach of the police but later de-arrested.
The unsavoury scenes follow similar incidents being witnessed at several Football League play-off matches recently – a fan was jailed for assaulting Sheffield United striker Billy Sharp after the team's defeat at Nottingham Forest earlier this week, while pitch invasions have also occurred at Huddersfield Town, Northampton Town, and Port Vale in recent days.