The 17-year-old Sunderland fan, who was held by Northumbria Police following yesterday's sell-out 1-1 draw between the Barclays Premier League rivals, was said to have turned up at Newcastle's training ground this morning.

Harper was not at training today, but a club official was there to hear the teenager, accompanied by his father, make a heart-felt apology.

His father was said not to have slept a wink and was "mortified", a source said.

"His intention was to apologise to the manager, the club and to Harper," the insider said.

"He sat down with a club official and he could not have been more humble and full of remorse."

The teenager was arrested after he ran on the pitch and was later released on police bail until March. Northumbria Police said inquiries were ongoing.

Newcastle declined to comment on the apology, as the club tried to draw a line under the events at the Stadium of Light, although Harper has spoken of his shock at being confronted on the pitch.

The 35-year-old was allegedly pushed to the ground in the aftermath of Asamoah Gyan's late equaliser for the Black Cats.

Harper told the Evening Chronicle: "I didn't see him until he was right on me.

"The supporter was detained by Sunderland fans after the incident, which was nice, and I heard he had been arrested.

"[Sunderland chairman] Niall Quinn apologised to me after the game. I would like to thank the supporters of both teams for their concerns afterwards."

The Football Association were today awaiting reports into the trouble.

A total of 24 arrests were made before, during and after the game, with rival fans clashing in ugly scenes on the final whistle.

The FA had a crowd control adviser present at the match and will consider his report and that of referee Howard Webb once they receive them.

An FA spokesman said: "We are awaiting reports this morning and will be proceeding from there."

Harper appeared to be barged to the ground as Gyan, his team-mates and the Black Cats fans among a crowd of 47,864 celebrated the Ghana international's stoppage-time strike.

Webb spotted the incident and guided stewards and police, and a youth was handed over by supporters and taken into custody.

The authorities will now consider the various reports and study footage of the trouble, as well as asking Sunderland for their observations.

However, the fact that the incident involving Harper was dealt with swiftly and the alleged offender was identified and arrested means the club is unlikely to face any FA sanctions.

Sunderland issued a club statement this morning promising to take action against anyone found guilty of offences, and praising supporters who helped to identify those responsible.

The statement said: "The vast majority of fans in the 48,000 capacity crowd behaved very well and we thank them for their loyal support.

"Sunderland AFC operates a zero-tolerance policy towards anti-social behaviour of any kind within the Stadium of Light, and we are proud of our reputation as a family club.

"Working closely with Northumbria Police, we will ensure that appropriate action is taken against anyone found to have been involved in any such behaviour at yesterday's game.

"The club also recognises the positive role Sunderland supporters played in helping to identify the small minority responsible for anti-social behaviour to stewards and the police."