Lewis Hamilton is set to take a five-place grid penalty at Sunday's Austrian Grand Prix after Mercedes changed the gearbox on his car.
As the previous unit has not completed six consecutive races, Hamilton will be served with a sanction that will come as a huge blow to his hopes of reeling in championship leader Sebastian Vettel this weekend.
An official report from FIA Formula One Technical Delegate Jo Bauer read: "[Hamilton] did finish the last race in Baku and this gearbox change was before the six consecutive events expired.
"As this is not in compliance with article 23.5a of the 2017 Formula 1 sporting regulations, I am referring this matter to the stewards for their consideration.
"The team informed the technical delegate about the gearbox change on Tuesday, 04th July 2017, at 11:29 hours."
The Formula One website describes the chances of Hamilton serving a penalty as "inevitable".
Hamilton, who trails Ferrari's Vettel by 14 points in the drivers' standings, was quickest in both practice sessions on Friday and has qualified on pole in Austria for the past two years.