England have reported Kamil Glik to the match referees after he appeared to pinch Kyle Walker's neck in the Three Lions' 1-1 draw with Poland on Wednesday night.
The Benevento defender appeared to pinch Walker's throat on the stroke of half-time as a free-kick was about to be played into the box before tempers boiled over when the whistle blew for the break.
The experienced Polish centre back and Harry Maguire were booked for their involvement in the tussle.
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England have reported the incident to FIFA with football's global governing body now on a factfinding mission to find out exactly what happened.
Southgate confirmed the report had been lodged post-match.
"There's been a report put in and we need to find out a little bit more about what's happened," he told BBC Radio 5 Live.
"At the moment we're still gathering all the evidence so there's no point in me speculating any further.
Kamil Glik (L) and Harry Maguire (R)
Image credit: Getty Images
Southgate was asked about the incident again in his post-match press conference, adding: "We're trying to find out exactly what happened and when we know more then we will let people know."
England draw means they lead the group by four points ahead of Albania, and will face Andorra away followed by Hungary at home in their qualifiers in October.
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