Newcastle have confirmed seven arrests and 22 ejections were made from St James' Park following crowd trouble during Saturday night's Premier League defeat to Liverpool.
And the club has warned it will take action against any fans who are found to have sold on tickets reserved for home fans to visiting supporters.
There were incidents of trouble both outside and inside the stadium for the match which Liverpool won 3-2 following a late strike from Divock Origi.
Newcastle officials said they would be investigating the circumstances which led to a number of visiting supporters apparently infiltrating areas of the stadium reserved for home fans.
Newcastle said in a statement: "Despite restricting match ticket sales to existing members and reminding fans that visiting supporters were not permitted in home areas, a number of Liverpool fans did obtain and use tickets initially held by Newcastle United fans.
"We can confirm that standard tickets were only sold by the club to existing Newcastle United members and no general admission tickets were sold to Liverpool supporters by Newcastle United beyond the visitors' usual allocation.
"We can confirm that 22 individuals were ejected from St James' Park on Saturday evening, with seven arrests made.
"We will be reviewing supporter feedback and CCTV and we will be taking action against any supporter who sold or passed on tickets to Liverpool fans.
"We remind supporters that selling or passing their tickets to other individuals is against ticket terms and conditions and may be a criminal offence."
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