Newcastle manager Eddie Howe has warned pitch invasions could lead to a "potential tragedy" as British police opened an investigation into an "altercation" involving Crystal Palace manager Patrick Vieira and an Everton fan.
Footage appears to show Vieira kicking out at the supporter, who was apparently taunting the former Arsenal and France midfielder after Everton secured their Premier League status with a dramatic 3-2 win on Thursday.
The Palace manager, who was surrounded by jubilant Everton fans celebrating their survival, refused to comment on the incident after the game.
Merseyside Police said in a short statement on Friday that they had begun a probe into the events at Goodison Park.
"We are working with Everton FC to gather all available CCTV footage and are speaking to witnesses," the force said.
"No formal complaint has been received and enquiries into the incident are ongoing."
Thursday's pitch invasion came on the same day a Nottingham Forest fan was jailed for headbutting Sheffield United captain Billy Sharp after Tuesday's Championship play-off semi-final, second leg.
There were also scenes of disorder at Port Vale on Thursday, with Swindon manager Ben Garner saying his players were "physically and verbally abused" after their League Two play-off semi-final defeat.
Newcastle boss Howe, whose side face relegation-threatened Burnley on the final day of the Premier League season on Sunday, said: "We have to act very quickly because we want to avert potential tragedy.
"The scenes at Nottingham Forest, I thought, were shocking to see and at Everton as well. I think we're going into dangerous territory where something could happen in a game that has terrible consequences, and I don't think anyone would want to see that."
- 'Alarming' -
The national head of football policing described the rise of pitch invasions as "alarming".
"The pitch is the players' place of work and like everyone else, they should be able to feel safe," said Chief Constable Mark Roberts.
"I know emotions are running high when clubs are getting promoted or avoiding relegation, but having large numbers of fans rushing onto the pitch at the end of the game is a safety risk for everyone."
Liverpool could win a league title with fans in the stadium for the first time since 1990 this weekend should Manchester City slip up at home to Aston Villa.
The Reds ended their 30-year title drought in 2020 behind closed doors due to coronavirus restrictions.
But Liverpool boss Jurgen Klopp urged supporters to control themselves against Wolves at Anfield, even if they do win the title.
"For the players of the other team it's massively uncomfortable and it should not feel dangerous for them," said Klopp. "We can celebrate things without threatening ourselves and the opponent."
Chairman of League One club Accrington Stanley, Andy Holt, has warned fans may end up bearing the cost for disorder in higher ticket prices to pay for enhanced security.
"Get a grip you complete clowns causing the problems," Holt posted on Twitter. "You win, you draw, you lose. If you can't cope with that STAY AWAY.
"You're ruining the day for many, increasing club security cost and as a result ticket prices for all."