Manchester United centre-back Jonny Evans and Newcastle United striker Papiss Cisse have been charged over allegations they spat at each other, the Football Association announced on Thursday.
The incident occurred during United's 1-0 Premier League win over Newcastle at St James' Park on Wednesday.
Evans has denied spitting at Cisse, but the Newcastle striker has issued a public apology for his behaviour. Both players could face six-game bans if the charges against them are proven.
"Newcastle United's Papiss Cisse and Manchester United's Jonny Evans have both been charged by The FA following their game on Wednesday 4 March 2015," the FA said in a statement on its website.
"The charges are in relation to an alleged breach of FA Rule E1[a] in that in or around the 38th minute of the game the two players spat at each other."
Cisse quickly accepted the FA charge, with Newcastle managing director Lee Charnley saying: "Both ourselves and Papiss agree that this kind of behaviour is not acceptable.
"In life, when you do something wrong you have to front up, admit your mistakes and accept the punishment.
"Papiss was proactive this morning in making a full and heartfelt apology, which he did in advance of any notification from the FA regarding this charge."
The incident occurred following a tangle between the players near the halfway line.
As the pair climbed to their feet, Evans seemed to spit towards the ground and Cisse appeared to react by spitting at the United defender's neck.
Referee Anthony Taylor did not take action against either player, but footage of the incident was reviewed by a three-man panel of former elite referees, who all agreed that both players should have been sent off.
In a statement on the United website, Evans said: "Having woken up this morning, I am shocked to have seen the media coverage from last night's match. I would like to make it clear that I did not spit at Papiss Cisse."
- 'I let you down' -
Evans added: "During the game Papiss Cisse and I spoke about the incident and it is clear by my reaction in the television footage that I was totally surprised by any suggestion of spitting.
"It is not in my character or in my nature to spit at anybody, nor is it something I have ever done or would ever do. It is certainly not something that I did last night."
In a statement of his own, Senegalese striker Cisse apologised to his Newcastle team-mates and the club's supporters, to Evans, and "to every football fan who saw the incident".
He added: "I reacted to something I found very unpleasant. Sometimes it is hard not to react, particularly in the heat of the moment. I have always tried hard to be positive a role model, especially for our young fans, and yesterday I let you down.
"I hope children out there playing football for their clubs and schools this weekend will know better than to retaliate when they are angry. Perhaps when they see the problem it now causes me and my team they will be able to learn from my mistake, not copy it."
United manager Louis van Gaal attempted to draw a line beneath the matter by backing Evans's claim that he had not spat at Cisse.
"He wasn't aware that he was spitting and when he was spitting on the ground, maybe that is a natural thing from a human being," the Dutchman told a press conference.
"It was not his intention and that I said already. I cannot imagine that Jonny Evans could do that and he has said that also. I believe him, so for me the matter has been done."