The Wall Street Journal with the report from Tuesday (may be gated).
Says that the US Securities and Exchange Commission is examining the relationship between the U.S. arm of Binance and "two trading firms with ties to Binance’s founder," The journal cites "people familiar with the probe".
- the firms are Sigma Chain AG and Merit Peak Ltd. (these are market makers that trade cryptocurrencies on the Binance.US exchange)
Check out the link for more on the details of the probe.
BTC update: