In this Aug 19, 2020 file photo, people wearing protective masks walk past signage for Hong Kong Exchanges & Clearing Ltd (HKEX) displayed at the Exchange Square complex in Hong Kong, China. (ROY LIU / BLOOMBERG)

A Hong Kong company whose board includes a brother of former US President George W. Bush plunged suddenly Friday, fueling speculation of a margin call.

Nearly 1.5 billion shares changed hands before Friday’s trading suspension, exceeding Hong Kong Finance Investment Holding Group Ltd’s free float of 923 million shares, according to data compiled by Bloomberg

Hong Kong Finance Investment Holding Group Ltd, whose operations include real estate and export of natural resources, slumped as much as 90 percent Friday morning before trading was suspended. The halt was at the firm’s request, it said in an afternoon stock-exchange filing, ahead of coming announcement about “a very substantial disposal of the company”. Chairman Hui Chi Ming controlled 64 percent of Hong Kong Finance as of June 30, according to its half-year report.

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Three traders who asked not to be identified because they’re not authorized to speak with the press earlier said margin calls are the likely reason for the shares’ sudden plunge. There’s a history of small stocks crashing without warning in Hong Kong, with margin calls often cited as a reason. Forced selling was behind April’s plunge in Car Inc shares. Last month, Singapore-based utilities contractor Wei Yuan Holdings Ltd plunged as much as 95 percent in Hong Kong in an unexplained move after posting huge gains.

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Hong Kong Finance’s vice-chairman is Neil Bush, younger brother to George W. Bush and former Florida Governor Jeb Bush. Shareholders are scheduled to vote on Oct 16 for what would be the firm’s third name change since 2013.

Nearly 1.5 billion shares changed hands before Friday’s trading suspension, exceeding the company’s free float of 923 million shares, according to data compiled by Bloomberg. There’s 4 billion shares outstanding. The stock had been falling steadily since early 2018, including a 39 percent drop this year through Thursday.