UPDATE 3-Soccer-Niang double puts Marseille point behind Lyon

* Olympique Marseille thrash St Etienne and go second

* Marseille one point behind leaders Olympique Lyon

* PSG stay in contention with Nice win

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By Julien Pretot

PARIS, April 5 (Reuters) - A Mamadou Niang double earned Olympique Marseille a 3-0 win at strugglers St Etienne on Sunday that left them breathing down Ligue 1 leaders Olympique Lyon's necks.

Senegalese Niang converted a penalty on the hour and put the result beyond doubt with 14 minutes remaining after fellow striker Brandao had doubled the tally on 74 minutes.

Marseille are second in the standings with 58 points, one less than Lyon with eight matches remaining after the champions won 3-1 at Le Mans on Saturday.

The result left St Etienne in 18th place, below the safety line.