The Latest on Uber's launch of self-driving cars in San Francisco (all times local):
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California regulators ordered Uber to stop its newly launched self-driving car service in San Francisco until it gets a state permit.
Uber started a public pilot program Wednesday morning, and hours later, the California Department of Motor Vehicles sent a letter warning legal action if the company didn't get the permit required for putting "autonomous vehicles" on public roads.
In a letter obtained by The Associated Press, DMV officials wrote that Uber "must cease" deploying the cars or face unspecified legal action.
Uber knew about the permit requirement but argued that its cars do not meet the state's definition of an "autonomous vehicle" because they require a person behind the wheel to monitor and intervene if needed.
Uber says that passengers in San Francisco can now use its app to summon a ride in a car that can drive itself.
While Wednesday's launch may set the tech-steeped city abuzz, it could also antagonize California regulators, who require permits for testing self-driving prototypes in public.
Uber interprets the rules differently, arguing it doesn't need a permit because a human still needs to be behind the wheel, monitoring the technology and ready to seize control.
The move into Uber's hometown builds upon a public pilot program the company started in Pittsburgh in September.
In San Francisco, Uber is deploying a "handful" of Volvo luxury SUVs that have been tricked out with sensors so they can steer, accelerate and brake, even decide to change lanes.