Volkswagen AG may face a U.S. Securities and Exchange Commission lawsuit over the carmaker’s failure to disclose to investors that its diesel vehicles didn’t comply with emission standards, according to a regulatory filing.

The SEC informed the German automaker that it might bring an enforcement action related to an investigation that formally began in January 2017, VW said Tuesday in its annual report. The probe relates to information the company didn’t disclose when it sold bonds and asset-backed securities.

VW’s American depositary receipts fell to a session low, dropping 2.6 percent as of 1:50 p.m. Thursday in New York.

Allegations that VW wrongfully withheld information about the emission software used in its diesel cars have loomed over the company since the scandal first broke in 2015. A German court is in the process of hearing a group action covering suits brought by thousands of investors with claims totaling more than 9 billion euros ($10 billion). The Braunschweig court has scheduled the next hearing in the case for March 25.

German prosecutors also are carrying out a criminal investigation into whether current Chief Executive Officer Herbert Diess, Chairman Hans Dieter Poetsch, and then-CEO Martin Winterkorn informed investors too late about VW’s diesel breaches and their potential impact years ago. The prosecutors will decide this year whether to pursue allegations of market manipulation against the trio. VW also said Tuesday that an administrative probe was opened against the company as part of the case.

VW has repeatedly said that it informed markets properly at all times, and the three managers have denied the allegations.