Ganfeng Lithium, one of China’s biggest lithium producers and an important Tesla supplier, is being investigated by Beijing’s top securities regulator for insider trading.Shares in Ganfeng Lithium dropped by as much as 7 per cent in Shenzhen after the company disclosed the probe by the China Securities Regulatory Commission for buying and selling a mainland-listed stock in the secondary market.No further details of the investigation were provided and the company declined to comment to the Financial Times, citing the ongoing investigation.The company said in a statement to the Hong Kong stock exchange that the CSRC decided to file a case...