Robinhood Markets Inc., the operator of the Robinhood equity and crypto trading app, revealed in its annual 10-K filing submitted to the Securities and Exchange Commission (SEC) that it received an investigative subpoena from the regulator in December 2022.

The subpoena is related to Robinhood’s cryptocurrency listings, custody of cryptocurrencies, and platform operations.

The SEC’s increased scrutiny of the cryptocurrency industry following a series of bankruptcies in 2022, including the collapse of Bahamas-based crypto exchange in November, prompted the subpoena.

Robinhood said it was cooperating with the SEC investigation and had received similar subpoenas from the California Attorney General’s office about its trading platform, business and operations, custody of customer assets, customer disclosures, and coin listings.

Robinhood’s filing highlighted the potential risks to the company should the SEC change its classification of a particular cryptocurrency to being a security.

Any particular cryptocurrency’s status as a “security” is subject to a high degree of uncertainty, and if Robinhood has not properly characterized one or more cryptocurrencies, it might be subject to regulatory scrutiny, investigations, fines, and other penalties.

The SEC fined U.S. crypto exchange Kraken $30 million in early February for offering its “staking as a service” program, which the agency said was in breach of the Securities Act. Kraken subsequently shut down its staking service.

The agency also charged cryptocurrency lender Genesis Global Capital and crypto exchange Gemini Trust in January, alleging the firms’ “Earn” lending program equated to offering and selling unregistered securities.