(Bloomberg) -- The Securities and Exchange Commission is investigating whether OpenAI investors were misled as the startup went through a ferocious debate over leadership last year, the Wall Street Journal reported, citing people familiar with the probe.

The US regulator is studying internal communications by Chief Executive Officer Sam Altman in relation to his ouster from the post in November, the report said. The SEC sent a subpoena to the company in December and asked senior OpenAI officials to preserve internal documents, according to the people.

To regain his job, Altman agreed to an internal investigation, among other conditions. The abrupt nature of his firing and a statement from the board saying that Altman hadn’t been “consistently candid in his communications” set up expectations for the emergence of a smoking gun. Nothing like that has come out, though there have been revelations of tensions within OpenAI over his fundraising for an outside chip venture, including seeking funding in the Middle East, and a dispute with former board member Helen Toner over a research paper she’d co-written that was critical of the company.

Read More: OpenAI’s Altman Ouster Was Result of Drawn-Out Tensions

It was Altman’s pattern of behavior, rather than a single egregious action, that caused the board to lose trust in him, according to a person with direct knowledge of the board’s thinking, who asked not to be named discussing private business matters.

OpenAI’s ChatGPT triggered the current rush to adopt artificial intelligence across all manner of industries and services, with Microsoft Corp. investing more than $10 billion into its partnership with the closely held startup.

The SEC’s probe may not lead to any finding of wrongdoing by the parties involved. OpenAI selected two lawyers from the firm WilmerHale to conduct its investigation into the events.

“While the review is ongoing, the board will continue to take steps to strengthen OpenAI’s corporate governance, build a qualified and diverse board of exceptional individuals, and oversee OpenAI’s important mission in ensuring that artificial general intelligence benefits all of humanity,” Bret Taylor, chair of OpenAI’s board, said in December.

(Updates with detail of Altman’s ouster from third paragraph)

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