South Yorkshire Police have pledged to work with both Leeds United and Sheffield Wednesday to find the supporter who invaded the pitch and assaulted Chris Kirkland in Friday night's game between the clubs at Hillsborough.
Kirkland, 31, appeared to be pushed in the face by a supporter who ran from the Leppings Lane End of the ground, which housed some 5,000 Leeds fans, in the aftermath of Michael Tonge's 77th-minute goal for the visitors.
The incident was one of a number of unsavoury ones to have occurred on a shameful night, which saw Leeds fans sing songs about criminal charges against Wednesday manager Dave Jones which were dropped in 2000, while they also appeared to herald former broadcaster Jimmy Savile, who is currently the subject of a child abuse investigation.
Bottles were also thrown onto the pitch from the away end, while home fans sang songs relating to the deaths of two Leeds fans in Turkey in April 2000. After the match, Jones branded the Leeds fans as "vile animals" and called for them to be banned from every away ground in the country.
And, in a statement issued on Friday night, South Yorkshire Police's chief superintendent Jason Harwin said: "During tonight's match, Sheffield Wednesday versus Leeds United, at Hillsborough incidents occurred where it is believed seats and bottles were thrown inside the ground.
"We are also aware of an incident whereby the Sheffield Wednesday goalkeeper has been assaulted by an individual who ran onto the pitch.
"Fans are still leaving the ground and surrounding areas and our priority is to ensure the safe departure of fans.
"Such incidents are not acceptable and won't be tolerated. We will be working with both clubs to identify and quickly bring to justice the persons responsible.
"Thankfully, such incidents are a rarity and we see a minority spoil it for the majority of genuine supporters."