The delayed disclosure of Elon Musk's Twitter stake under the inspection of regulator

Elon Musk, the chief executive of SpaceX and Tesla, has been investigated for his tardy 

submission of a public form that investors must file when they buy more than five percent of a company, 

The Wall Street Journal reported Thursday, citing people familiar with the matter.

Since January, Musk has been buying Twitter shares, and by March 14 he had a five 

percent stake in the microblogging site. As per Securities and Exchange Commission (SEC) guidelines, 

Musk should have notified the regulator after reaching five percent within ten days of securing the stake. 

In fact, he missed the deadline and filed with the SEC only on April 4.