Hong Kong shares of BYD Co Ltd recorded their worst day in 20 months on Tuesday after Citibank’s increased holding of the Chinese EV firm’s stock sparked market chatter that Warren Buffett’s Berkshire Hathaway may have cut its stake. Citibank’s shareholding in BYD has increased by 225m shares to 388.61m shares on July 11 from 163.4m shares on July 8, disclosures from HKEX’s Central Clearing and Settlement System regarding market intermediaries showed. Top holder Berkshire Hathaway owned 225m shares, or about 20.5pc of BYD at the end of 2021, according to Refinitiv data. “The size is a good match with Warren Buffett’s stake in BYD,” a director at a regional brokerage said, adding it fuels speculation Buffett might have cut his stake, with the shares sitting in the custodian bank. Berkshire did not immediately respond to a request for comment and Citibank declined to comment. Reuters could not independently verify speculation around Buffett’s change in stake. Big investors have to disclose major changes to their shareholding and so far, there is no information on that, BYD said in response to a Reuters request for comment on WeChat. BYD shares dropped nearly 12pc to HK$270.20. The company overtook Tesla Inc in global electric vehicle sales in first half of 2021, according to a media report last week.