Much of the leverage used by Hwang’s Archegos Capital Management was provided by banks including Nomura Holdings Inc. and Credit Suisse Group AG through swaps or so-called contracts-for-difference, according to people with direct knowledge of the deals. It means Archegos may never actually have owned most of the underlying securities -- if any at all.

While investors who build a stake of more than 5% in a U.S.-listed company usually have to disclose their position and subsequent transactions, that’s not the case with stakes built through the type of derivatives apparently used by Archegos. The products, which are made off exchanges, allow managers like Hwang to amass stakes in publicly traded companies without having to declare their holdings.

The swift unwinding of Archegos has reverberated across the globe, after banks such as Goldman Sachs Group Inc. and Morgan Stanley forced Hwang’s firm to sell billions of dollars in investments accumulated through highly leveraged bets. The selloff roiled stocks from Baidu Inc. to ViacomCBS Inc., and prompted Nomura and Credit Suisse to disclose that they face potentially significant losses on their exposure.