Formula 1 teams faced fresh fuel system checks at the Monaco Grand Prix as part of a clampdown by the FIA.
The issue of trick fuel systems has been a big talking point all season, with Motorsport.com revealing at the Spanish Grand Prix that the FIA issued a technical directive to ensure teams were not finding ways to exploit the rules.
One suggestion was that some teams could be cleverly storing fuel beyond the fuel flow meter, perhaps in expanded pipes, and then throwing the excess in to the engine for a power boost when it was needed for acceleration.
The FIA had said that it reserved the right to carefully examine each team's fuel system, and that is why further detailed examinations took place after the first free practice session in Monaco on Friday.
One car from Mercedes, Renault, Ferrari and Honda was checked.
All within the rules
A note from the FIA said: “The fuel system downstream the FIA fuel flow meter was checked on car numbers 44 (Lewis Hamilton), 03 (Daniel Ricciardo), 05 (Sebastian Vettel) and 14 (Fernando Alonso).”
The FIA also analysed the fuel pressure of all the cars.
FIA technical delegate Jo Bauer confirmed that the checks had uncovered nothing untoward, with the governing body stating that all teams were within the regulations.