DETROIT (Reuters) - General Motors Co GM.N Chief Executive Mary Barra said on Thursday the automaker will expand testing of self-driving vehicles to Michigan, and will build its next generation of self-driving cars in the Michigan plant that builds the Chevrolet Bolt electric car.

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Separately, Barra declined to discuss a statement by a Chinese government official that a U.S. automaker could be subject to penalties for price-fixing.

“I don’t think anyone benefits from speculating on that,” Barra told reporters at the event in GM’s downtown Detroit headquarters.

China is GM’s largest single market, accounting for 37.6 percent of the automaker’s global vehicle sales during the first nine months of 2016, compared with 31 percent for the United States.

Chinese officials did not name the automaker in their comments to the official China Daily.

Investors sold down shares of GM and rival Ford Motor CoF.N on Wednesday after the statement, which was seen by analysts and foreign policy experts as a warning by Beijing to President-elect Donald Trump not to upset the status quo in relations between the two countries.

GM has been accelerating its efforts to deploy self-driving cars, earlier this year buying autonomous driving startup Cruise Automation. GM and Cruise engineers have been testing self-driving prototypes in Arizona and California.

Rivals, including Ford Motor CoF.N, Uber Technologies [UBER.UL] and AlphabetGOOGL.O Inc's Waymo self-driving car unit, are also testing autonomous vehicles on public roads in various states and countries.

Barra used a press conference at the company’s Detroit headquarters to show off an electric Chevrolet Bolt equipped with roof-top sensors designed to enable autonomous driving.

GM executives have said the automaker could eventually deploy self driving electric cars in fleets managed by its ride services partner, Lyft. However, Barra did not address Lyft in her remarks Thursday.

GM said it will start building a “next generation” of autonomous vehicles at the factory in Orion Township, Michigan north of Detroit early next year. That factory builds Chevrolet Bolts and Chevrolet Sonic subcompact cars.