Blanc is being questioned today as part of an inquiry which was launched after a French website released a transcript of a meeting last November, in which Blanc allegedly discussed introducing quotas for the number of dual-nationality players at youth training centres.
A number of players have been trained at French youth academies in recent years, only to switch sides and play for other national teams when they are old enough.
François Blaquart has already been suspended as technical director of the French national team, in connection with the row.
Members of France's famous multi-racial 1998 World Cup winning side have now joined the controversy.
Lilian Thuram and Patrick Vieira have both strongly criticised Blanc, but Christophe Dugarry, Marcel Desailly, Bixente Lizarazu, and the coach in 1998, Aimé Jacquet have rallied to his defence.
Asked on Saturday if Blanc's words in the meeting were discriminatory, Zidane said: "No, and concerning Laurent, let's be straight and clear: I know him well, of course he's not racist. I'll go even further; he never even thinks like that because it's not an issue for him. I think that's why he got drawn into a discussion like that."
Laurent Blanc took over as coach of the French national team last year, with the task of rebuilding the national side following the debacle of the 2010 World Cup in South Africa, when the team staged a strike, before being eliminated after the first round, and returning home in disgrace.
The current squad is top of its Euro 2012 qualifying group, and surveys show that very few French people want Laurent Blanc to resign over the matter.
71 per cent want him to stay on, 22 per cent have no opinion, and only seven think he should stand down.