The U.S. Securities and Exchange Commission has published its first warning against initial exchange offerings (IEOs) Tuesday.

According to the notice, the regulator considers IEOs to be similar to initial coin offerings (ICOs), many of which the agency has been investigating as unregistered securities offerings for the past several years. While IEO providers may claim their sales are different from ICOs, they may still violate federal securities laws, the SEC said. As such, the agency warned investors to "be cautious" if they are considering investing in an IEO.

"IEOs are being touted as an innovation on ICOs because they are offered directly by online trading platforms on behalf of companies – usually for a fee – to provide immediate trading opportunities for the digital assets," the notice said.

However, the SEC took aim at crypto exchanges directly, noting they "are typically not registered with the SEC" and "may improperly refer to themselves as 'exchanges.'"

The SEC warned a platform saying it is registered does not necessarily mean it is actually registered with the agency, and it emphasized that "there is no such thing as an SEC-approved IEO."