Strasbourg - Sebastien Ogier took the lead at his home Rally of France on Friday as Citroen team-mate Sebastien Loeb looks set to be forced to retire with engine problems.
Loeb won the opening stage in his native Alsace and had led after the first two stages before his car ground to a halt during special stage three.
And the French driver, who is on the cusp of an eighth world rally title, admitted that he could be forced out of this 11th leg of the 13-rally season.
"For the moment the engineers aren't saying much, they say that there was a swift drop in oil pressure, and they will have to examine it, but it's not very encouraging for tomorrow (Saturday)," said Loeb.
"We couldn't believe it because we're not used to that," he continued.
"The car always worked well, we've never had mechanical problems since the start of the season.
"Everything looked to be going well, it was sunny, the roads dry, I was leading and it ends quite badly."
Ogier won stages two and three to take a five-second advantage on Norwegian team-mate Petter Solberg after the first four stages with Spaniard Dani Sordo third at 6.6 seconds in a Mini John Cooper Works.
Special stage three proved no better for Citroen's arch-rival Ford, as both Loeb's leading title rival Mikko Hirvonen and Jari-Matti Latvala went off the road but were able to continue and are sixth and seventh respectively.
Finland's Kimi Raikkonen crashed his Citroen warming his tyres before SS3.
Loeb leads the overall standings with 196 points, Hirvonen is second on 181 with Ogier third on 167.