Southampton and West Brom fans appeared to throw missiles at each other as the Saints celebrated booking their places in the Championship play-off final.
Russell Martin's side dominated the second leg clash at St Mary's on Friday evening, winning 3-1 on the night and aggregate thanks to a Will Smallbone strike and brace from Adam Armstrong.
They will take on Leeds at Wembley next weekend as both sides aim for an immediate return to the Premier League following relegation last season.
After the full time whistle, hundreds of home fans invaded the pitch to celebrate their side reaching the final, and appeared to goad away supporters before scenes turned ugly.