DETROIT -- Dan Ammann, CEO of General Motors' Cruise autonomous vehicle subsidiary, is leaving the Detroit company.

       GM didn't give a reason in a short statement Thursday but said that Kyle Vogt, president and chief technical officer, would be Cruise's interim CEO.

       The leadership change comes just as Cruise is about to start a fully autonomous ride-hailing service without human safety drivers. GM product development chief Doug Parks said last week that commercial autonomous ride-hailing would start next year in San Francisco.

       Ammann was GM's president until November of 2018 when the company sent him to San Francisco to lead Cruise, where he replaced Vogt as CEO. He was GM's chief financial officer before being promoted to president in 2014. Ammann, a former Morgan Stanley investment banker, joined GM as treasurer in 2010 to help lead its public stock offering after emerging from government-funded bankruptcy protection.

       When Ammann moved to Cruise, many analysts believed that GM was preparing for a public stock offering with the majority-owned subsidiary.

       But last week Parks dismissed that speculation, saying that GM believes the companies create more value as a combined entity.

       GM's statement says that combined, GM and Cruise create a large manufacturing and technological scale for autonomous vehicles “that will rapidly drive costs down.” The company says the integration will maximize the market for autonomous vehicles.

       In extended trading, GM shares slipped 2.4%.