The Brazilian Grand Prix weekend is barely under way but already three drivers, including championship contender Lewis Hamilton, are under investigation. The McLaren man, Honda's Jenson Button and Super Aguri's Takuma Sato apparently used more than the allowed sets of wet tyres in Friday morning's practice.

It was a difficult session with the track officially declared wet; the regulations state that a driver may not use more than one set of wet and one set of extreme wet tyres during practices one and two. Hamilton, Button and Sato are reported to have used two sets of wets during the first session.

Hamilton finished fifth fastest overall, Button was 12th and Sato 14th so it's debatable if using the extra sets of tyres gave the drivers an advantage. All three are expected to appear before the stewards after the second practice session and it is at the stewards' discretion to decide what penalty, if any, should be imposed.