Renault-Nissan chairman Carlos Ghosn reportedly faces arrest.

Japanese media say he's being questioned over under-reporting his salary, and will be detained.

The Asahi newspaper says prosecutors have started searching Nissan's headquarters.

The Japanese firms says it's already moving to terminate Ghosn's contract.

It says it has discovered several serious acts of misconduct, including using company money for personal purposes.

Renault shares tumbled 13 percent on the news.

SOUNDBITE (English) IG SENIOR ANALYST, CHRIS BEAUCHAMP, SAYING: "Without that magic touch at the helm the future of these companies look a lot more difficult so I think the shares will remain under pressure for the foreseeable future." Ghosn is a legend in the industry - one of very few foreign top executives in Japan.

He's generally revered there for reviving Nissan from near bankruptcy.

Ghosn became chief executive of the company in 2001, when Renault bought a controlling stake.

He held the post until last year, when he became chairman.

Records show he received 9.2 million euros for his final year as boss of the Japanese firm.

He got another 7.4 million for running Renault that year.