French investigators are preparing to go to Saudi Arabia soon as part of their probe into incidents targeting French nationals that have marred the Dakar sports car rally, a source with knowledge of the matter said on Friday. French anti-terrorism prosecutors opened a preliminary investigation earlier this month into an explosion under a support vehicle at the rally at the end of December, in which French race driver Philippe Boutron was seriously injured. They have also heard from witnesses about a second incident in which a support truck, belonging to the team of Franco-Italian rally competi…