A detailed investigation by FIA staff who visited Red Bull's Milton Keynes factory has concluded that the squad did not use its controversial front bib adjuster in an illegal manner, Autosport can reveal.
Red Bull had found itself at the centre of intrigue in recent weeks over a tool it had tucked away in its car to raise and lower its tea tray.
Rival teams were concerned that the adjuster could have been used to alter the height of its front bib between qualifying and the race – which would be a breach of parc ferme rules.
When the issue first erupted ahead of the United States Grand Prix, the FIA moved quickly to add a seal to the device so that it could not be adjusted once the cars were in parc ferme.
But that did not stop questions from some rivals who felt that potential historical use of the system needed looking at to be sure that Red Bull had not broken the rules in the past.
The FIA insisted however that there was no evidence it had been used illegally and that it would be difficult to try to check on previous use over the past couple of years.
Its single-seater director Nikolas Tombazis said in Austin: "To go and retroactively actually prove exactly what has happened before is difficult, and we don't think we have the ability to go and investigate two years' worth of situation.
"I mean, honestly, can I say with complete certainty about whether there's ever been anything irregular? No. Can I say that the matter is closed? Yes, absolutely."
That was not enough to quell the concerns from Red Bull's competitors though, with both McLaren and Mercedes expressing unhappiness over the situation and urging the FIA to do more to be certain that nothing untoward had taken place.
McLaren CEO Zak Brown called on the FIA to interview Red Bull staff to dig deeper into the matter, while Mercedes boss Toto Wolff said he anticipated intervention from FIA president Mohammed Ben Sulayem.
Asked about the FIA's initial claim of it being a 'closed' matter, Wolff said: "I cannot speak for the FIA at all. I cannot speak for Nikolas. Obviously, that's something that's been not spotted for a long time.
"But I think the leadership of the FIA is going to look at that, and say, 'What are we doing with this?'"
Following this lobbying, it is understood that the FIA duly agreed after the Brazilian Grand Prix to launch a more formal investigation to be sure that Red Bull was not hiding anything.
That culminated in a visit to the team's Milton Keynes factory last week by senior FIA personnel to look in detail at the situation surrounding the front bib adjuster.
Sources have indicated the visit included looking at data, the car, design drawings and speaking to relevant personnel.
Following that visit, the FIA has now said that Red Bull has been given the all-clear and that the governing body is satisfied the device was never used outside the regulations.
In a statement, it said: "The FIA regularly reviews and inspects the conformance to the technical, sporting and financial regulations of the F1 teams, and this may involve spot-checks at the circuit or inspections and investigations at the teams' factories.
"Similarly, it is the prerogative of the F1 teams to bring to the attention of the FIA any concerns about the compliance of their competitors' with the regulations, and this phenomenon is clearly intensified in championships where there may be closer competition for the ultimate prize, as has been the case in 2024.
"The FIA takes any such issues very seriously and seeks to investigate them in addition to all the regular checks it carries out during a race weekend and beyond.
"As part of this assessment process, FIA technical representatives visited the Red Bull Racing headquarters to investigate in-depth recent allegations about their front floor design and its use. This investigation concluded that no breach has taken place, and therefore confirmed the position adopted by the FIA during the US Grand Prix in Austin."
Tyre cooling matter closed too
As well as the controversy over Red Bull's front bib adjuster, the FIA has also found itself involved in technical intrigue over alleged tyre cooling tricks.
Suspicions emerged ahead of the Brazilian Grand Prix that several teams could have been injecting water into their tyres to help cool them – which would improve their performance over race stints.
The allegations are understood to have emerged amid claims that moisture and water marks were seen within some wheel rims after tyres had been stripped following the Singapore Grand Prix.
The FIA conducted investigations on this matter in Brazil, with Tombazis personally checking on tyres and rims as they were taken apart after the sprint race at Interlagos.
With there being no evidence of anything untoward being found, the FIA has also concluded that it is satisfied no teams were breaking the rules on this front.
An FIA statement added: "In parallel, the FIA investigated during the last grand prix in Brazil recent allegations that competitors may have used water to manage overheating of tyres. No evidence was found to suggest any irregular behaviour.
"We consider both matters closed, but will continue to monitor the situation in detail."
