Former Nissan Chairman and Renault CEO Carlos Ghosn remains locked in a Japanese jail cell after Tokyo prosecutors filed new charges against the legendary auto executive earlier this month. But as the French government begins to question the terms of his detention while raising questions about his living conditions in detention, rumors that Ghosn's downfall was engineered by restive elements within Nissan - led, many believe, by CEO Hirohito Saikawa - have continued to simmer, spurred by a New York Times story published late last year that included speculation that Ghosn's ouster was part of a coup.

But as the Japanese automaker struggles to move on from the scandal, its executives are experiencing unprecedented backlash thanks to suspicions surrounding the provenance of the "internal probe" that eventually led to Ghosn's arrest. And now, the allegations that Ghosn and another executive (American Greg Kelly, who was also arrested and charged) conspired to underreport the income of the man who created the Nissan-Renault-Mitsubishi alliance have drawn an SEC investigation.

According to Bloomberg, the US securities regulators is investigating whether Nissan’s executive-pay disclosures were accurate and whether the carmaker maintained adequate controls to prevent improper payments. Because Nissan shares trade in the US using ADRs, the SEC believes it has jurisdiction over the automaker, despite that most of the activities under investigation took place in Japan and Europe. Nissan shares slid nearly 3% on Monday after the company confirmed that it will cooperate with the probe.

The Wall Street Journal, which initially broke the story, reported that because the SEC has broad authority to bring penalties, Ghosn and Nissan could eventually face fines or charges in the US.

The SEC investigation ramps up pressure on the carmaker, has been indicted in Japan, which will allow prosecutors to lay out formal charges. But the involvement of a foreign regulator means the Ghosn scandal has officially gone international.

The SEC inquiry, launched out of its Washington headquarters, is focused on whether lapses by Nissan in reporting on its executives’ pay violated U.S. securities law, one of the people said. The regulator’s work was slowed by more than a month of partial U.S. government shutdown, another said. While the SEC’s civil inquiry is in its early stages and may not point to wrongdoing, it adds a layer of complexity for Nissan and the two former executives. The SEC, which often works closely with law enforcement, could seek financial penalties and injunctions to prevent violation of laws or SEC rules. John Nester, a spokesman for the SEC, declined to comment. Aubrey Harwell Jr., an attorney for Kelly, said his client hasn’t received an SEC subpoena and declined further comment. U.S.- and Japan-based representatives for Ghosn declined to comment. In a memo to staff last month, Nissan Chief Executive Officer Hiroto Saikawa, who succeeded Ghosn as CEO, said oversights in the company’s corporate governance “permitted the situation to continue, which clearly calls for grave reflection.”

Ghosn and Kelly were indicted in Tokyo for conspiring to underreport Ghosn's income. Ghosn has also been indicted for allegedly shifting trading losses on to Nissan's books. Kelly, a Tennessee resident who was once known as the "Ghosn whisperer", was released on bail last month and has pledged to remain in Japan. Ghosn allegedly conspired to avoid reporting income that had been set aside for his retirement. Prosecutors claim the income should have been disclosed in the company's financial statements. Ghosn has spent more than two months in a Tokyo jail.

And according to the latest round of charges, it appears that he could remain there for a while longer. But if the SEC has its druthers, it looks like he and Kelly might not be the only executives who could wind up in hot water.