Football's world governing body Fifa has started disciplinary proceedings against Mexico after claims of racism by their fans during their World Cup match against Cameroon last Friday.
In a statement Fifa said the inquiry was launched after what they called improper conduct by Mexican fans.
Fifa sources told the BBC they are also looking into alleged discrimination by fans from Brazil, Russia and Croatia.
Tough new rules to stop such offences were introduced by Fifa last year.
A first racism offence by fans or players can be punished by having to play a game behind closed doors - subsequent or more serious offences can be punished by deducting points, relegation or expulsion from a competition.
It is alleged that Cameroonian players were subjected to racism during their 13 June match against Mexico
Leading Fifa executives have repeatedly stated that financial sanctions have no deterrent effect.
Fifa is also believed to be looking into reports of homophobic chanting by Brazil's supporters and anti-Semitic and racist banners displayed by followers of Croatia and Russia.