Citic Pacific Ltd faces a formal investigation from the Hong Kong Securities and Futures Commission after predicting HK$15.5 billion in currency losses from unauthorized trades.

A probe has started, the commission said on its website, without elaborating. Hong Kong Exchanges & Clearing Ltd, which runs the city's bourse, is also "looking into" whether the company complied with listing rules, said Henry Law, a spokesman.

Citic Pacific has slumped 66 percent in the past two days and its debt ratings were cut after the company disclosed on Oct 20 the impact of wrong-way bets on the Australian dollar.