Facebook and the Federal Trade Commission (FTC) are in negotiations over a settlement that would result in a massive fine of multiple billion dollars for privacy violations, the Washington Post reported Thursday afternoon. The fine would be the largest such penalty ever by the agency against a technology company.

Facebook and the FTC didn’t immediately respond to a request for comment Thursday.

The FTC officially began investigating Facebook last March. At the time, the acting director of the FTC’s Bureau of Consumer Protection Tom Pahl had said that “the FTC takes very seriously recent press reports raising substantial concerns about the privacy practices of Facebook.”

The agency’s investigation has not been public, but it is thought to have focused on a series of privacy violations conducted by Facebook, including the Cambridge Analytica scandal that resulted in the Trump campaign-linked company gaining access to private data from millions of Facebook users.

At issue for the agency was also the question of whether Facebook violated a previous consent decree with the FTC, which required the company to get consent from its users before sharing data. The consent decree came with a potential fine of up to $40,000 per violation. “Companies who have settled previous FTC actions must also comply with FTC order provisions imposing privacy and data security requirements,” Pahl said at the time.

Facebook investors seemed to shrug off news of the potential fine Thursday. The company’s share price was down just 0.4% in after-hours trading.