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."
The situation had been complicated by video footage of Vettel's dashboard display and trackside flags that appeared to contradict each other.
Vettel overtook Vergne on lap four while his dashboard display showed the yellow-flag warning sign, meaning overtaking is not allowed.
However, on board videos appeared to show a marshall waving a green flag on the inside of the track.
"The request for a clarification from the FIA, regarding Vettel's passing move on Vergne, came about through the need to shed light on the circumstances of the move, which came out on the Internet only a few days after the race," Ferrari said in a statement on their website (www.ferrari.com).
"The letter to the FIA was in no way intended to undermine the legality of the race result. We received tens of thousands of queries relating to this matter from all over the world and it was incumbent on us to take the matter further, asking the Federation to look into an incident that could have cast a shadow over the championship in the eyes of all Formula 1 enthusiasts, not just Ferrari fans.
"Ferrari duly takes note of the reply sent by the FIA this morning and therefore considers the matter now closed."