(Bloomberg) -- Talos Energy Inc., a US oil producer whose biggest shareholder is billionaire Carlos Slim, slid after the unexpected departure of its chief executive officer.

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Tim Duncan, who was also one of the company’s founders, stepped down on Thursday, Talos said in a statement that didn’t provide a reason for his exit. Board member Joseph Mills will serve as interim CEO, and Talos has hired an executive search firm to find a permanent successor. Shares slid as much as 10.3% in New York, the biggest intraday tumble since November.

Earlier this month, Carlos Slim, Latin America’s richest person, took advantage of the equity-market selloff to boost his stake in Houston-based Talos, which focuses on oil exploration and production in the Gulf of Mexico. Slim’s family holding company owned about 22% of Talos as of Aug. 7, data compiled by Bloomberg show.

Duncan’s departure came as news to the Slim family, according to a representative.

“We had no prior notice he was about to leave the company and have no further comment,” Arturo Elias Ayub, a family spokesman, said in a text message.

Tim Rezvan, an analyst at KeyBanc Capital Markets, called Duncan’s exit a surprise — and a negative. Rezvan wrote in a note to clients that KeyBanc spoke with the company and learned the board, after becoming concerned about Talos’ share performance, decided new leadership was needed to rebuild credibility with investors.

Before the announcement of Duncan’s exit, Talos was down 16% this year, compared with a 3% gain for the S&P Oil and Gas Exploration and Production index. Talos reaffirmed third-quarter production guidance as well as its full-year view on operational and financial results in Friday’s statement.

“We appreciate the unchanged 2024 outlook, but admit to having less confidence on the 3Q outlook following this news,” Rezvan wrote. The analyst said he wonders whether other issues factored into the management change, including the company’s operations in the field as well as differences over acquisition strategy and how to address Slim’s growing position. Talos didn’t immediately return phone and email messages seeking comment.

Neal Goldman, Talos’ board chair, said in the statement that the company has “complete confidence in Joe’s capabilities to carry out Talos’ strategy as we search for a new CEO to lead Talos into the future and unlock further value.”

Mills joined the board in March after Talos acquired the closely held Gulf producer QuarterNorth Energy Inc., where Mills was a director.

(Updates with comment from Slim family representative in fourth paragraph)

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