Stewards at the Singapore grand prix on Sunday confirmed that Sebastian Vettel broke the pitlane speed limit by just 1.4kmh during the race.
The Red Bull driver and championship challenger was at the time challenging the lead of Lewis Hamilton's McLaren, but after serving a drive-through penalty he finished fourth with a mountain to climb to now win the title.
Vettel, 22, said he did not consciously surpass the 100kmh pitlane limit and was surprised when told by radio that he had breached the rules.
"From my point of view, I wasn't in a rush and therefore I can't really explain why I got caught -- we'll have to check if it's maybe an electronic issue, but (the speed limiter) was working before and afterwards so it's difficult to say.
"There's a bit of a question mark there," the German added.
