The U.S Securities and Exchange Commission (SEC) is investigating Elon Musk's delayed disclosure of his sizable stake in Twitter Inc last month, the Wall Street Journal reported on Wednesday, citing people familiar with the matter.

The SEC and the Tesla Inc top boss did not immediately respond to Reuters' requests for comment.

On April 4, Musk disclosed a 9.2% stake in Twitter, making him the micro-blogging site's largest shareholder. A week later, he clinched a $44 billion deal to buy the company.

Separately, the Information earlier reported that the Federal Trade Commission is investigating whether Musk violated a law that requires companies and people to report certain large transactions to antitrust-enforcement agencies.

  - Reuters