A U.S. investigation into the collapse of Bill Hwang’s Archegos Capital Management is examining whether the firm engaged in market manipulation.

The U.S. Securities and Exchange Commission is scrutinizing the firm’s trading activity, including whether it concealed the size of its bets on public companies, according to people familiar with the matter. Authorities are reviewing whether Archegos bought multiple stakes in the same companies across several banks in an effort to avoid triggering public disclosure rules. In aggregate, Hwang’s positions were massive. 

The opening of an SEC probe is typically a preliminary step and doesn’t mean Hwang, who hasn’t been accused of wrongdoing, will face an enforcement action. Representatives for Hwang and the SEC declined to comment.

Archegos amassed a concentrated portfolio of stocks well in excess of US$100 billion by using borrowed money. It imploded in March as some of the stocks tumbled, triggering margin calls from banks, which then dumped Hwang’s holdings. 

Lenders including Credit Suisse Group AG, Nomura Holdings Inc. and Morgan Stanley lost more than US$10 billion, prompting internal investigations and the forced departures of senior executives. Regulators, meanwhile, are discussing whether to revise rules exempting family offices like Hwang’s from tougher oversight.

SEC Chairman Gary Gensler told Congress in May that more stringent disclosure laws may be warranted for investment firms after the Archegos debacle, and he later signaled plans to make more industry data publicly available.

The fiasco has drawn public criticism from global regulators as well as inquiries from watchdogs around the world. The Department of Justice has also opened an investigation into the firm’s collapse.

This isn’t the first time Hwang has been the subject of a market-manipulation probe. 

In 2012, after years of investigations by authorities in the U.S. and Hong Kong, the SEC accused his former firm, Tiger Asia, of insider trading and manipulation of Chinese bank stocks. Hwang settled that case without admitting or denying wrongdoing, and Tiger Asia pleaded guilty in the U.S. to wire fraud. At that point, Hwang closed his firm and opened Archegos.

It’s unclear what’s left of Hwang’s fortune, and anything that remains may be scraps for others. Banks have said they plan on trying to recoup money from Archegos, its related entities and individuals.