A hooligan who ran on to the pitch and assaulted a goalkeeper during a Championship football match has been identified by police.
The suspect, who has been named on social media sites but not by police, has yet to be arrested after former England goalkeeper Chris Kirkland was shoved in the face amid ugly scenes at the game between Sheffield Wednesday and Leeds United at Hillsborough on Friday night.
The FA is also investigating crowd trouble at the Yorkshire derby and is awaiting the referee's report.
The attacker can be seen dashing round the goal, after knocking down Kirkland
Kirkland, who was playing for Sheffield Wednesday, was assaulted by the Leeds fan after the visitors had equalised.
The shocking scenes were broadcast live on Sky Sports and fans were quick to condemn the trouble on Twitter and Facebook. That led to a suspect being named on sites, and a mobile phone number being circulated.
South Yorkshire Police's senior investigating officer, Detective Inspector Mark Monteiro, said: "With the public's assistance we have clearly identified the offender who ran on to the pitch during last night's game between Sheffield Wednesday FC and Leeds United FC and who is suspected of assaulting the Sheffield Wednesday goalkeeper.
"We are dealing with the complaint made by the player and we are currently taking statements, collating evidence and making inquiries to locate and arrest the offender.
"We are also using CCTV footage from around the ground to identify suspects who may have been responsible for other offences before, during or after the match.
"I'd like to thank the supporters and general public who have provided information and assisted with our inquiries."
An FA spokesman said: "We have begun an immediate investigation and have been in contact with both clubs.
"We would call for the authorities to identify and bring before the courts anyone who was involved in any form of criminal disorder."
Kirkland required medical treatment before he could continue.
Police said there were five arrests for various offences including public order before and after the game, while three people were ejected from the ground and 12 were subject to dispersal orders.
Leeds issued a statement after the game pledging to identify the man involved in the incident.
It read: "Leeds United Football Club would like to publicly apologise and condemn the action of the fan who came on the pitch and attacked Sheffield Wednesday goalkeeper Chris Kirkland.
"The club will fully co-operate with the police and the football authorities in identifying the individual concerned.
"After the week football has endured there is no place for this type of behaviour and the majority of Leeds supporters will be ashamed of his actions."
The match was also marred by vicious chanting from some Leeds fans about Wednesday manager Dave Jones, who was cleared of child abuse allegations in 2000.
Wednesday fans replied with songs about two Leeds fans killed in Turkey in April 2000. Leeds supporters responded by throwing bottles on to the field and clashing with police.
Jones called for Leeds fans to be banned from "every away ground".
Anyone with information is asked to call police on 101 or Crimestoppers on 0800 555 111.