The US Securities and Exchange Commission is investigating whether Coinbase Global Inc improperly permitted Americans to trade digital assets that should have been registered as securities, Bloomberg News reported on Monday.

In an emailed response to Reuters, a Coinbase spokesperson said the company does not list securities on its platform.

The cryptocurrency platform has previously asked the SEC to develop rules that work for digital asset securities.

“We think there’s a huge untapped market and the US risks falling behind if the SEC doesn’t engage in a transparent and public rulemaking process for digital asset securities,” the spokesperson added.

The US regulator did not immediately respond to Reuters’ request for a comment on the Bloomberg report. The probe by the SEC’s enforcement unit predates the agency’s investigation into an alleged insider trading scheme that was revealed last week, according to the report.

US prosecutors in Manhattan charged a former product manager at Coinbase and two others last week with wire fraud in the first insider trading case involving cryptocurrency, with Ishan Wahi, the product manager at the cryptocurrency exchange, and his brother Nikhil Wahi arrested in Seattle.

The SEC, in related civil charges, had alleged that Nikhil Wahi and another defendant Sameer Ramani had sold at least 25 crypto assets for a profit, nine of which the agency identified as securities.

An SEC official declined to say at the time whether it would pursue action against Coinbase for listing the tokens deemed securities in the complaint.

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The regulatory scrutiny of Coinbase has increased ever since the platform expanded the number of tokens in which it offers trading, the report added, citing two sources.