Speculation is rife that Warren Buffet’s Berkshire Hathaway is about to dump its $7.7 billion stake in Chinese automaker BYD.

The car manufacturer saw its shares fall by 12 percent after a stake close to the size of Berkshire Hathaway’s appeared in the Hong Kong stock exchange’s clearing system. Nikkei Asia reports that BYD shares registered in the clearing system rose by 225 million on Monday, almost all of which came from accounts with Citigroup.

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“The number of Berkshire shares coincides with the number deposited with Citibank,” a head of an unnamed Hong Kong brokerage company said. “The implication is Berkshire might dump the stock…it’s psychologically very disturbing for the market when this kind of news comes in.”

BYD itself says no statement has been given to the Hong Kong exchange revealing that a major stakeholder was changing its holding in the company, something that’s required under local regulations.

Berkshire Hathaway owned a 7.7 percent stake in BYD as of February, valued at approximately $7.7 billion. This represents a more than 33-fold gain over its initial $232 million investment made in 2008. BYD’s shares have performed well in recent months, soaring by more than 100 percent since March and touching a high of HK$333 ($42) in late June.

Neither Berkshire Hathaway nor Citigroup has commented on the reports.

Word of Buffet potentially selling his BYD stake comes just a week after it emerged that the automaker had sold 641,350 New Energy Vehicles in China during the first half of the year, consisting of EVs, PHEVs, and hydrogen vehicles. That placed it ahead of Tesla which sold 564,000 EVs in the first half of the year. BYD had a particularly strong June where it produced 134,771 NEVs and sold 134,036 NEVs.