The head of the Securities and Exchange Commission told Sen. Elizabeth Warren that the cryptocurrency realm needs further regulation and that Congress should give the agency a corresponding rule-making authority.

SEC Chairman Gary Gensler told Warren, a Massachusetts Democrat, in a letter released Wednesday morning that he shared her interest in ensuring investor protection on cryptocurrency exchanges and emphasized that he doesn’t think that those investors are adequately protected right now. He said that the SEC has taken and will continue taking its regulatory authority as far as it’s permitted.