Red Bull's Sebastian Vettel committed no infringement during the season-ending Brazilian Grand Prix, Formula One's governing body the FIA said on Friday, meaning the German keeps his world title.
The 25-year-old clinched his third straight championship on Sunday after finishing sixth in Brazil to leave him three points clear of Ferrari's Fernando Alonso.
Ferrari, however, wrote to the FIA in the aftermath of the race to seek official clarification of whether Vettel had illegally overtaken Toro Rosso's Jean-Eric Vergne.
Had a protest been upheld, Vettel could have been dropped to eighth in the race and Alonso would have been world champion by one point.
"The FIA received a letter from Scuderia Ferrari, seeking clarification on Sebastian Vettel's overtaking manoeuvre in Sao Paulo on Sunday," the FIA said in a statement.
"In the spirit of transparency and goodwill, the FIA wishes to make public the receipt of this letter.
"The Federation also informs it has replied to Scuderia Ferrari, in the same constructive spirit, stating that as the overtaking manoeuvre was not in breach of the regulations, and therefore there was no infringement to investigate, it was not reported to the stewards by race control."