The U.S. Securities and Exchange Commission has reportedly launched a probe into major crypto exchange Binance’s U.S. arm regarding trading firms connected to Binance CEO Changpeng Zhao.

According to a Tuesday report from the Wall Street Journal, the SEC is looking into the relationship between Binance.US and trading firms Sigma Chain AG and Merit Peak. The federal regulator has reportedly requested information from the U.S. crypto exchange on the two companies, and is investigating how it may have disclosed its potential links to the market makers to users.

The news outlet reported that corporate documents from 2019 as well as former Binance executives connecte Zhao to both trading firms. Sigma Chain AG and Merit Peak, acting as market makers, both continuously buy and sell crypto on Binance.US, which usually reduces price volatility.

It’s unclear how the SEC might proceed with any enforcement action even if it confirmed an investigation was underway. Cointelegraph reported on Jan. 20 that the regulator brought 97 enforcement actions with $2.35 billion in penalties between 2013 and 2021 against crypto firms, including Poloniex and Blockchain Credit Partners.

Related: SEC hits BlockFi with a $100 million penalty, gives 60 days to comply with a 1940 law

In May 2021, Binance was reportedly under investigation from both the Department of Justice and Internal Revenue Service in an attempt to stop U.S. residents from using crypto for illicit transactions. A report from March suggested that the Commodity Futures Trading Commission was also investigating the major crypto exchange regarding the activity of U.S. users. Binance CEO Changpeng Zhao denied any allegations of misconduct at the exchange at the time.

Cointelegraph reached out to Binance.US and Binance, but did not receive a response at the time of publication.