(Reuters) -BYD Co shares sank nearly 12% on Tuesday after a large stake matching the size of Berkshire Hathaway (NYSE:BRKa) Inc's investment in the Chinese electric car company appeared in Hong Kong's clearing system.
The development prompted speculation that Warren Buffett's company might be reducing its multi-billion-dollar stake in BYD.
A 225 million share BYD stake entered Hong Kong's Central Clearing and Settlement System, with Citigroup Inc (NYSE:C) serving as custodian.
Berkshire acquired its own 225 million BYD shares in 2008, giving it a 7.73% stake, according to BYD's annual report.
The stake also represents 20.49% of BYD's total issued H shares, the report said.
Berkshire did not immediately respond to a request for comment. Citigroup declined to comment.
BYD said it had no information on whether Berkshire was reducing its stake, but that large shareholders must disclose major changes to their holdings.
Berkshire has said it paid $232 million for its BYD shares, whose value is now about $7.7 billion despite Tuesday's decline.
The shares have approximately doubled in price since May 2021.
Electric vehicle sales in China have been rising in recent months, benefiting from government measures to spur demand.
BYD overtook Elon Musk's Tesla (NASDAQ:TSLA) Inc as the world's largest seller of electric vehicles in the first half of this year, according to sales data from the companies.
Buffett, who is Berkshire's chairman and chief executive, has not signaled concern about BYD that might prompt selling.
His reputation is a reason investors often buy and sell the same stocks they know or suspect Berkshire is buying or selling.
Buffett has said his business partner Charlie Munger was the impetus for the BYD investment.
BYD shares closed Tuesday down HK$36.60 at HK$270.20.