OpenAI investors are pushing to bring back Sam Altman as CEO one day after he was ousted by the board, according to people familiar with the matter says CNBC.

Microsoft, Tiger Global and venture firm Thrive Capital are among several of OpenAI’s top backers that are part of an effort to reinstate Altman, said a source, who asked not to be named because discussions are confidential.

Sequoia Capital has also been in contact with Altman, a person familiar with knowledge of the matter told CNBC. Sequoia supports Altman and former OpenAI president Greg Brockman in whatever they choose to do next, whether it’s returning to OpenAI or creating a new startup, the person said. Sequoia also informed Microsoft that it would back efforts to bring back Altman and Brockman, the person said.

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The Verge first reported on the talks to bring back Altman. The publication, citing a source, said Altman is “ambivalent” about returning and would demand governance changes. Altman didn’t immediately respond to CNBC’s request for comment. Nor did Thrive. Microsoft declined to comment.

OpenAI’s announcement late Friday that the company was firing Altman and replacing him on an interim basis with technology chief Mira Murati sent shockwaves across Silicon Valley. OpenAI has emerged as the hottest startup on the planet since launching its ChatGPT chatbot last year and spurring a rush of investment generative artificial intelligence market. The company had reportedly been in talks as recently as last month to sell employee shares at a valuation of $86 billion.

Microsoft, which has invested billions of dollars in OpenAI and has a close technology partnership with the company, was surprised by the announcement. In addition to ousting Altman, the company removed Brockman, the chairman, from his board leadership position but said he would remain as president. Brockman said later in the day that he quit.