Lululemon Athletica Inc. said its chief executive, Laurent Potdevin, resigned after unspecified behavior that failed to meet the company’s standards, an abrupt exit that surprised investors of the fitness apparel maker.

The company said Monday afternoon that Mr. Potdevin, who had been its top executive since January 2014, had resigned as CEO and a board member, effective immediately. The Vancouver-based company has started a search for a new CEO.

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