Washington - US regulators are looking into Susquehanna International Group’s allegations that unknown insider traders made US$100 million (S$130 million) on options bets ahead of a recent Chinese regulatory crackdown on cross-border brokerages Futu and Tiger Brokers, according to a person familiar with the matter.Susquehanna went public with its claims in a lawsuit filed on June 29 in Manhattan federal court. The US Securities and Exchange Commission (SEC) is examining the trades described in the market-making firm’s complaint, said the person.Pennsylvania-based Susquehanna said in its suit that it lost more than US$70 million as counterparty on most of the alleged insider trades. According to the complaint, the traders bought US exchange-traded options in Chinese securities firms that were subsequently targeted in a May 22 crackdown.The scope and stage of the SEC’s probe weren’t immediately clear and the regulator’s reviews can end without any enforcement action being taken. The SEC declined to comment.Susquehanna sued 100 John Doe defendants, acknowledging it did not know who made the trades, but it said “high risk, high reward” options bets could only be plausibly explained as insider trading.A federal judge later on June 29 granted Susquehanna’s request for an order freezing accounts at Interactive , Brokers Group and the platforms of Futu and Tiger Brokers’ parent company Up Fintech Holdings, hat the defendants allegedly used to make their trades. Susquehanna was also given permission to subpoena the firms for the account-holders’ identities.Futu and Tiger Brokers were also two of the firms targetted by the Chinese government, which said they were operating unlicensed trading services for mainland residents. Shares in both fell sharply on the May 22 announcement. Futu was hit with a 1.85 billion yuan (S$353 million) regulatory penalty, and founder Leaf Li saw his fortune drop by US$1.7 billion in a single day on the stock drop. A spokesperson for Interactive Brokers said it had been cooperating with Susquehanna, including freezing accounts, and would “cooperate with relevant regulators as we receive inquiries.” In its lawsuit, Susquehanna said the alleged insider traders were likely tipped off by Chinese regulatory staff or workers at Futu or Up. They were able to buy the options cheaply, spending around US$12 million to generate a profit of at least US$100 million, Susquehanna said.Susquehanna, which is active in options, stocks, energy, bonds and foreign exchange markets, said in an SEC filing that its equity positions in the first quarter totaled more than US$893 billion. The market-making firm has made its co-founder Jeff Yass one of the richest people in the world with a fortune estimated at US$93 billion, according to the Bloomberg Billionaires Index. BLOOMBERG