March 8 (Reuters) - OpenAI Chief Executive Sam Altman

will return to the ChatGPT-maker's board along with three new

directors, the world's most prominent artificial intelligence

company said on Friday.

An investigation into the events surrounding the

November firing of Altman also has concluded, and the company

has created new governance rules including strengthening its

conflict of interest policy.

Employees, investors and OpenAI's biggest financial backer,

Microsoft ( MSFT ), had expressed shock over Altman's ouster,

which was reversed within days.

The company appointed new directors including Altman, Sue

Desmond-Hellmann, a former CEO of the Bill and Melinda Gates

Foundation, Nicole Seligman, a former president of Sony

Entertainment, and Fidji Simo, CEO of Instacart.

The investigation by law firm WilmerHale found that a

breakdown in trust between the board and Altman led to his

firing. Altman's dismissal was not the result of concerns

related to OpenAI's finances, product safety or other issues,

WilmerHale determined.

"WilmerHale found that the prior Board believed at the

time that its actions would mitigate internal management

challenges and did not anticipate that its actions would

destabilize the Company," OpenAI said in a blogpost.

The board's lack of detail for its surprise November

decision fueled speculation about potential misconduct by

Altman, which he and the company have denied, and about supposed

existential risks from the technology that OpenAI is building.

Altman's return as CEO about four days after his firing came

after nearly all of OpenAI's employees threatened to depart

unless the board restored Altman and resigned.

His return led to discussions about how OpenAI would be

governed, and the company announced a reconstituted board that

did not include Altman. It was helmed by Silicon Valley

entrepreneur Bret Taylor.