Towards the end of Luton's 3-2 win, referee Sam Allison stopped the game in additional time to speak to both sets of managers after Luton and Morris made a complaint.

Morris was seen speaking with fourth official Andy Madley before play resumed.

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Asked about the incident after the game, Luton manager Edwards said in his press conference: "It's an alleged racial comment, the police are dealing with that now. They've spoken to Carlton and got his take on it, it's with them now so I've got no more comment on it.

"Carlton's alright. At the time, he seemed pretty angry but he seems fine now."

Luton Town confirmed Morris reported abuse at Bramall Lane, while the Premier League said: "Racism has no place in our game or anywhere in society and we encourage anyone who hears or sees discrimination to report it so action can be taken.

"We will offer our full support to Carlton Morris and Luton Town FC, as well as continuing to work with clubs and authorities to ensure our stadiums are an inclusive and welcoming environment for all."

Speaking to Amazon Prime, Morris did not reveal what was said by the individual in the front row in the main stand of Bramall Lane.

"The Premier League have been great at telling us protocols and things like that, and I heard something from the crowd in the front row, unfortunately," he said.

"I thought it was best to get it reported straight away, and then go from there."

Kick It Out has said that anyone found guilty of racially abusing Morris must face "the strongest possible consequences".

They issued a statement on Wednesday morning which read: "We send our full support to Carlton Morris. It's shameful that once again a player should be subjected to alleged racism while doing their job.

"Morris should be praised for how he handled the situation, and we commend the clubs, police and officials for their swift approach. But it should never have to come to this.

"Those who think this vile behaviour towards players is acceptable need to face the strongest possible consequences."

Sheffield United manager Chris Wilder said in his own press conference: "There was a comment which was made that the referee came over to speak to me and Rob [Edwards] about, from a racial point of view which obviously is not great if found to have been the case.

"It was from the crowd, towards one of their players."

A statement from the Blades read: "Sheffield United FC is disappointed to learn of an alleged racist incident, late in the game during the Premier League Boxing Day fixture against Luton Town.

"Once the club had been aware of the alleged incident, an investigation was instigated, and we are now in dialogue with South Yorkshire Police and Luton Town FC, and we thank both for their assistance.

"The club would like to again reiterate we take a zero-tolerance approach to racism and stands firmly against all forms of discrimination. There is no place for this behaviour in football, or society as a whole.

"The incident came in a game where referee Allison became the Premier League's first Black referee in 15 years, following Uriah Rennie's spell as a top-flight official ending in 2008."