PARIS (Reuters) - Paris prosecutors opened a manslaughter investigation following the death of Christophe de Margerie, the head of French oil group Total, in a plane crash in Russia, a judiciary source told Reuters on Tuesday. Separately, French accident investigation agency BEA said it would participate in Russia's Total air crash inquiry, sending three investigators to Moscow later on Tuesday. De Margerie was killed when his private jet collided with a snow plough as it was taking off from Moscow's Vnukovo airport on Monday night. (Reporting by Marine Pennetier, Tim Hepher,; writing by Michel Rose)