Certain exchanges that facilitate initial exchange offerings (IEOs) may be breaking U.S. securities laws, a top Securities and Exchange Commission official has said.

Speaking Monday at CoinDesk's Consensus 2019 conference in New York, Valerie Szczepanik, the SEC's senior advisor for digital assets and innovation, said cryptocurrency exchanges that facilitate token sales for a fee likely meet the legal definition of securities dealers if the issuer or any of the buyers are based in the U.S.

As such, they need to follow the registration and licensing requirements for broker-dealers, alternative trading systems (ATS) or national securities exchanges. And if they're not, they're going to be in hot water, according to Szczepanik.

“Platforms seeking to list these tokens for a listing fee or bring buyers to the table for issuers are probably engaging in broker-dealer activity," Szczepanik said during a chat with Bloomberg reporter Matthew Leising, adding:

Szczepanik did not mention any specific exchanges. However, Binance, OKEx, Bittrex and KuCoin are among the exchanges that have facilitated IEOs, and these transactions are believed to be generating millions of dollars in fees for such platforms.

The most famous platform for IEOs is Binance's Launchpad, which in January hosted a public sale of BitTorrent tokens, raising $7.4 million for the file-sharing service owned by Tron.

Szczepanik said a previous case brought by the SEC last year against TokenLot "was instructive in this regard."

"There was a platform that was assisting to bring buyers to ICOs," she said. "In this case, there was an enforcement action, as the platform was acting as a broker-dealer and participating in the distribution with a violation of the registration provisions.”

Watch CoinDesk's IEO explainer below:

Valerie Szczepanik, right, at Consensus 2019 image via Anna Baydakova for CoinDesk.