Stewards were investigating whether the Mercedes driver, who won from 14th on the grid, illegally crossed a line separating the entry from the track when he hurriedly changed his mind about pitting during a safety car period.
Hamilton, who could be handed a time penalty if found guilty of the offence, finished 4.5 seconds ahead of Finnish team mate Valtteri Bottas and 6.7 clear of Ferrari's third-placed Kimi Raikkonen.
Raikkonen collected a five-second penalty in Azerbaijan two years ago for a pitlane offence.
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Lewis Hamilton (Mercedes) a signé une victoire magistrale et capitale à Hockenheim.

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However race director Charlie Whiting, speaking as stewards continued their deliberations, told reporters that incident was "quite a lot different" and he could not recall any other direct precedent.
Whiting said the stewards would have to decide whether Hamilton had acted in an unsafe manner or not.
The summons came more than an hour after the end of the race at Hockenheim, after the podium presentations and news conferences.
One of the stewards was Finnish former Ferrari driver Mika Salo, who collected the best result of his career when he finished second for the Italian team at Hockenheim in 1999.

Lewis Hamilton lors du Grand Prix d'Allemagne 2018

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Hamilton's victory had catapulted him 17 points clear of Ferrari's Sebastian Vettel, the home favourite who crashed out while leading on a wet and slippery track.
"I started turning in, then they asked me to box and then I said ‘Kimi is pitting’ and then they said ‘Stay out’ and I was already in the lane," Hamilton told reporters after the race when asked what had happened.
"So I started turning out and trying to go over the grass and then they said ‘no, stay in!’ and I was already back on track.
"It was really confusing because they were all panicking on the pit wall, I was probably the only relaxed one," he said. "They were shouting ‘yes, no, come in, don’t come in’. It was exciting."
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