SHANGHAI (Bloomberg) -- Toyota Motor Corp. and Honda Motor Co.'s Chinese ventures joined Daimler AG's Mercedes-Benz unit and Volkswagen AG's Audi brand in reducing prices of spare parts amid an antitrust investigation into the auto industry. GAC Toyota Motor Co., the Japanese maker's venture with China's GAC Group, will cut prices on some components from Aug. 18, according to statement on its Web site. Guangqi Honda Automobile Co., Honda's venture with GAC, will lower some parts prices from Sept. 1, according to a separate statement. China, the world's largest auto market, is stepping up scrutiny over how much foreign carmakers charge for vehicles and spare parts. The government began looking into possible antitrust violations in the auto industry at the end of 2011 as state media accused manufacturers of inflating prices and overcharging consumers. BMW AG will reduce prices on more than 2,000 components by an average of 20 percent starting Aug. 11, the automaker said Thursday. Daimler plans to cut spare-part prices for its Mercedes-Benz vehicles in China by an average of 15 percent starting next month, while Audi's Chinese joint venture said in late July that the brand would lower replacement costs of its parts by as much as 38 percent on Aug. 1. Antitrust officials in eastern Jiangsu province have begun investigations of Mercedes-Benz dealers in five cities including Suzhou and Wuxi, while Mercedes-Benz's Shanghai office was raided by local officials of the National Development and Reform Commission, NDRC spokesman Li Pumin said in a briefing in Beijing on Wednesday. The government will also soon punish Chrysler Group and Audi for engaging in monopolistic actions, he said. The NDRC is undertaking the investigation to protect the competitive order of the auto industry and safeguard consumer interests, Li said at the briefing. The commission has completed an investigation into 12 Japanese companies and will soon announce the actions it will take, he said.