WASHINGTON—State and provincial regulators in the U.S. and Canada said they have conducted a wide-ranging crackdown on initial coin offerings throughout the past several weeks, resulting in nearly 70 open investigations and 35 pending or completed enforcement actions.

As part of a coordinated action plan dubbed “Operation Cryptosweep,” the regulators said they went after dozens of initial coin offerings, or ICOs, whose popularity in recent months has made them popular vehicles to solicit funds from investors. An initial coin offering is a process by which a company, typically a tech startup from the digital-currency sector, creates a new virtual coin or token and offers it for public sale.

“The actions announced today are just the tip of the iceberg,” said Joseph Borg, president of the North American Securities Administrators Association, at a press briefing Monday announcing the operation, which commenced at the beginning of May.

The Wall Street Journal last week reported that a review of documents for 1,450 coin offerings found that hundreds of technology firms used deceptive or even fraudulent tactics to lure investors, including plagiarized investor documents, promises of guaranteed returns and missing or fake executive teams.

The probe ratchets up the regulatory pressure on the multibillion-dollar U.S. market for raising funds in cryptocurrencies. It follows a series of warnings from the top U.S. securities regulator suggesting that many token sales may be violating securities laws.