Real Madrid were on Friday punished for the behaviour of their fans during the second leg of the Champions League playoff against Manchester City.
In the decision, Uefa, the governing body of European football, found Real's fans guilty of "discriminatory behaviour".
Neither the television footage nor journalists present reported any incidents during Madrid's 3-1 home victory on 19 February over Manchester City that sent the reigning champions through to the last 16.
The statement said the fans had violated article 14 of Uefa's disciplinary regulations, which punishes "racism, other discriminatory behaviour and propaganda".
Uefa fined Real €30 000 and also threatened the club with a partial closure of "at least 500 adjacent seats" at the 78 297-capacity Santiago Bernabeu stadium if there are further incidents in the next two years.
Several dozen national teams and clubs are currently subject to the same suspended sanction, including Real's two main rivals in Spain, Barcelona and Atletico de Madrid, for similar offences.