Securities regulators are investigating a company’s $50 million cryptocurrency sale, an executive with the firm said, and people familiar with the probe said it includes looking at whether a prominent bitcoin entrepreneur broke the law by getting involved with the company’s fundraising.

The entrepreneur, Erik Voorhees, is chief executive of ShapeShift AG, a digital-asset exchange that suspected criminals have used to launder millions of dollars in allegedly ill-gotten gains, The Wall Street Journal reported earlier this year....