Middlesbrough manager Gareth Southgate believes a 'line was crossed' by Newcastle fans who allegedly abused striker Mido at the weekend.
The 24-year-old Boro striker was a target for sections of the travelling support in the 2-2 draw in the Tees-Tyne derby and was booked for the manner of his celebration when he scored in the 28th minute - his second goal in as many games since signing from Tottenham.
The Football Association have promised to speak to both teams as they investigate the treatment of Mido, whose abuse was said to include some Islamophobic chanting.
Southgate believes all professional footballers expect a certain degree of interaction with supporters but believes the Egyptian forward was put through an unacceptable ordeal.
He told Radio Five Live: 'I don't know if it will ever be resolved. All players accept that when they go on the field of they will be ridiculed and people will try to goad them.
'But there is a line and that line was crossed at the weekend.'
Southgate conceded his striker had reacted to the crowd but insisted the club were fully supportive of him.
He added: 'He (Mido) is a human being and he reacted. But I am very much in his corner and we want to draw a line under it.'
An FA spokesman earlier confirmed the governing body would be looking into Sunday's events.
'We will be contacting both clubs for their observations on these events and we will take it from there,' said the spokesman.
Boro will be taking no further action over the chants, which they hope will not be repeated by supporters of other teams.
Club spokesman Dave Allan said: 'We very much hope that there is no repeat of these chants in the future, but as far as we are concerned, the matter is now closed.'
Newcastle were not commenting on the matter today.
Mido's booking was one of eight in a fiercely-contested match, fraught with local rivalry.
Former Boro striker Mark Viduka signed for the Magpies on a free transfer in the summer and scored his first goal in a Newcastle shirt, and his 150th in British football - against his former employers.
Meanwhile, Julio Arca - who used to play for Wearside club Sunderland - scored to seal a draw for the hosts.