Uefa has told BBC Scotland that they will investigate allegations of bigoted chanting from Rangers fans during their Champions League ties with Villarreal.
The Villarreal team bus arrived with a smashed window
Rangers also face a disciplinary hearing over an incident that led to the Villarreal team bus being attacked.
A Uefa spokeswoman said: "We are looking into complaints of possible bigoted chanting from both legs of the tie involving Rangers and Villarreal."
A Uefa panel will discuss both charges on 12 April.
And a statement on the Uefa website said: "The European governing body will give attention to the improper conduct and hooliganism of Rangers supporters in the return leg in Spain on 7 March, as well as to the fans' discriminatory chants in both fixtures.
"Villarreal are also being investigated for lack of organisation and violation of Uefa security instructions in the return leg match."
Rangers will be given the opportunity to respond in writing before the hearing.
"Rangers Football Club are aware of the disciplinary proceedings instigated against us in respect of fan behaviour at both the home and away Villarreal matches," read a statement from Ibrox.
"Whilst taking the allegations levelled by Uefa extremely seriously, it would be inappropriate to discuss these matters at this stage."
The Spanish side had their team bus attacked prior to the 1-1 draw at the El Madrigal Stadium.
"Rangers fans broke a window on the team bus when the players were still on board," a Villarreal spokesman said.
"It was a frightening experience for them but thankfully no-one was injured."
And Rangers have already criticised security arrangements for Tuesday's match.
With 15,000 Scots travelling to Spain and only 3,000 tickets officially allocated, thousands gained admission to the home end.
Club safety chief Lawrence McIntyre said: "All my worst fears came true. There was poor stewarding and the police were taken by surprise."
Rangers bowed out of the competition on the away-goals rule, following a 2-2 draw at Ibrox in the first leg.
McIntyre added: "There was an excess of fans for the stadium and people without tickets and there was some crushing.
"The infrastructure for a match of this magnitude was not good enough.
"There were no serious injuries but people were traumatised.
"Experienced Rangers travellers said they have never seen anything like it. There was serious crushing."