Several hundred home supporters ran on to the Fir Park pitch after Motherwell’s 3-0 second-leg win on May 31, which clinched a 6-1 aggregate victory.
Many ran in the direction of the away stand to taunt the Rangers fans before returning to the stands as police horses prepared to enter the surface.
The Scottish Football Association has dealt with a brawl involving players.
Former Rangers defender Bilel Mohsni, who has now signed for French Ligue 1 side Angers, was banned for seven games while several Motherwell players - Craig Moore, Lionel Ainsworth and Fraser Kerr - were given two-match bans.
The SPFL is responsible for incidents involving supporters and it has said little on the subject of the game. However, investigations are ongoing.
Doncaster said: “We’re continuing to look at that particular game and there may be something to announce in due course.
“When we’re in a position to make a comment further, then we’ll do so. It’s not closed.”