A US regulator says it is watching events at Twitter with “deep concern” after the platform’s top privacy and compliance officers reportedly quit. The Federal Trade Commission (FTC) said new chief executive Elon Musk was “not above the law”.

The Federal Trade Commission is closely watching Twitter’s moves under new owner Elon Musk, a spokesperson said in a statement Thursday. The agency struck a settlement with Twitter earlier, which granted it oversight of certain security and privacy practices at the company.

“We are tracking recent developments at Twitter with deep concern,” an FTC spokesperson said in a statement. “No CEO or company is above the law, and companies must follow our consent decrees. Our revised consent order gives us new tools to ensure compliance, and we are prepared to use them.”

The statement comes after several key security and privacy executives resigned or were dismissed from the company following Elon Musk’s $44 billion acquisition of Twitter.

According to internal communications obtained by CNBC, three execs involved in information security, privacy and compliance all resigned in recent days, including Kissner. In the message, a worker warns that the FTC can and will fine Twitter billions of dollars if it breaches the consent decree. The author of the message advised peers they could reach out to Twitter’s ethics helpline or the FTC if they felt uncomfortable with tasks they are assigned.

The message reminds workers that Twitter’s former security chief Peiter “Mudge” Zatko reached out to nonprofit law firm Whistleblower Aid to go public with complaints about Twitter’s security practices. Whistleblower Aid also represented Facebook whistleblower Frances Haugen and received funding from a foundation run by eBay founder Pierre Omidyar, who has been a major critic of the Big Tech firms.