UEFA have opened disciplinary proceedings against Atletico Madrid and Bolton following the crowd trouble at last week's UEFA Cup tie in Spain.
Official reports have been submitted to the UEFA Control and Disciplinary Body, which will decide on the matter at its next meeting on Thursday, March 20.
Spanish police said the problems at the match were "just the usual at any football game" and refused to respond to Bolton's allegations.
Greater Manchester Police, whose Chief Superintendent David Lea was in the stadium to witness the Spanish police's behaviour, insist Bolton fans were not at fault and pledged to help the club compile a report to UEFA.
This is not the first time this season complaints have been made about Spanish police at the same venue, with Aberdeen writing to UEFA in November after they felt their fans were mistreated during their group game against Atletico.
Spain's own anti-violence commission has already recommended fines and bans for Atletico and certain supporters regarding incidents inside and outside the Vicente Calderon.