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Nissan Chairman Carlos Ghosn, one of the auto industry’s most high-profile executives, has been arrested in Japan after an internal investigation revealed “significant acts of misconduct” over many years by him and another top executive.

The stunning announcement ripped through a powerful global alliance, slamming the stocks of Nissan (NSANY) and Renault (RNSDF), where Ghosn also serves as chairman.

Together with Japan’s Mitsubishi Motors (MMTOF), Nissan and Renault make up the biggest global carmaking alliance, which makes one of every nine cars sold around the world. The three companies employ more than 470,000 people in nearly 200 countries.

Nissan said in a statement that it had been investigating Ghosn, a 40-year veteran of the auto industry, and another board member for months following a whistleblower report.

“These two gentlemen were arrested this evening, that is what I understand,” Nissan CEO Hiroto Saikawa said at a press conference in Tokyo late on Monday.

Japanese prosecutors confirmed the arrests of Ghosn, 64 and the other board member, Greg Kelly, on suspicion of violating financial laws by filing false statements. According to the prosecutors’ statement, the two men allegedly collaborated to under-report Ghosn’s income by about 5 billion yen ($44 million) over a five-year period ending in March 2015.

CNN wasn’t immediately able to reach Ghosn, Kelly or their representatives for comment.

Carlos Ghosn at a Renault factory in France earlier this month. He oversees an alliance between the French automaker and Japan's Nissan and Mitsubishi Motors.

The maximum punishment in Japan for filing a false financial statement is up to 10 years in prison and a fine of up to 10 million yen ($89,000).

Nissan said its internal investigation also found “numerous other significant acts of misconduct … such as personal use of company assets.”

As a result, CEO Saikawa will propose to Nissan’s board of directors to “promptly remove Ghosn from his positions as chairman and representative director,” at a meeting on Thursday, the company said. He will also try to have Kelly removed from the board.

Renault and Nissan shares plunge

Shares in Renault, where Ghosn is chairman and CEO, closed down more than 8% in Paris. Renault said its board would convene “very shortly” to discuss Nissan’s revelations.

French President Emmanuel Macron said the government, which owns 15% of Renault, was watching closely.

“The state, as a [Renault] shareholder, will be extremely vigilant regarding the stability of the alliance and the group,” Macron said during a visit to Belgium.

Nissan’s announcement came after the close of trading in its stock in Tokyo on Monday. Its shares were down around 5% on Tuesday morning.

“Nissan deeply apologizes for causing great concern to our shareholders and stakeholders,” the company’s statement said. “We will continue our work to identify our governance and compliance issues, and to take appropriate measures.”

Ghosn is also chairman of Mitsubishi Motors. The Japanese company said it was proposing that its board “promptly” remove Ghosn from that position. Its shares fell about 7% in Tokyo on Tuesday morning.

Under Ghosn, the three carmakers formed an alliance that rivals Volkswagen (VKLAF) and Toyota (TM) in terms of vehicle sales. The alliance sold 10.6 million vehicles last year.

Nissan said last year that it paid Ghosn a salary of 1.1 billion yen ($9.7 million) in the year ended March 2017, his last as CEO. Nissan doesn’t break out individual board members’ compensation in its annual report.

A career spanning continents

Born in Brazil, Ghosn started his career at French tire maker Michelin in 1978, working his way up to running the company’s North American operations.

He moved to Renault in 1996. After the French carmaker established its alliance with Nissan in 1999, he became the Japanese firm’s chief operating officer, helping steer it out of financial crisis.

The turnaround earned him the nickname “Le cost killer.”

Ghosn was promoted to CEO of Nissan in 2001, and then made the unusual move of taking on the role of Renault CEO in 2005. That made him the first executive to run two Fortune Global 500 companies at the same time.

After Nissan took a 34% stake in Mitsubishi Motors in 2016, Ghosn handed off the Nissan CEO role to Saikawa.

Yoko Wakatsuki, Charles Riley and Pauline Lockwood contributed to this article.