Japanese media say Carlos Ghosn, Nissan Motor Co. chairman, is being questioned by Tokyo prosecutors on suspicion he falsified his financial reports.
Nissan said Monday it was looking into the reports, while prosecutors declined comment.
The Asahi newspaper said Ghosn submitted voluntarily to questioning about suspected violations of financial and exchange regulations. The national broadcaster NHK and Kyodo carried similar reports.
Asahi said Ghosn is suspected of failing to report hundreds of millions of yen (millions of dollars) in income.
Nissan, based in Yokohama, Japan, said it was checking into the reports.
Brazilian-born Ghosn, sent in by alliance partner Renault SA of France, has led a dramatic turnaround at Nissan over the last two decades, rescuing Nissan from near-bankruptcy.