Six-times Formula One world champion Lewis Hamilton was under a stewards' investigation before the start of the Russian Grand Prix on Sunday for making a practice start outside the designated area.

The Mercedes driver qualified on pole position and is chasing his 91st career win, to equal the all-time record of Ferrari great Michael Schumacher.

Hamilton is leading team mate Valtteri Bottas in the championship by 55 points after nine races.

(Reporting by Alan Baldwin, Editing by Catherine Evans) ((alan.baldwin@thomsonreuters.com; +442075427933;))