WASHINGTON (REUTERS) - The US Securities and Exchange Commission (SEC) has sent subpoenas to Tesla regarding chief executive Elon Musk's plans to take the company private and his statement that funding was "secured", Fox Business Network reported on Wednesday (Aug 15), citing sources.

Subpoenas typically indicate the SEC has opened a formal investigation into a matter.

Tesla and the SEC declined to comment.

Musk stunned investors and sent Tesla's shares soaring 11 per cent when he tweeted early last week that he was considering taking Tesla private at US$420 a share and that he had secured funding for the potential deal.

The electric carmaker's shares were last down 1.9 per cent at US$341.00 on Wednesday.

They have erased all their gains following Musk's tweet last week.

Musk provided no details of his funding until Monday, when he said in a blog on Tesla's website that he was in discussions with Saudi Arabia's sovereign wealth fund and other potential backers but that financing was not yet nailed down.

The CEO's tweet may have violated US securities law if he misled investors.

On Monday, lawyers told Reuters Musk's statement indicated he had good reason to believe he had funding but seemed to have overstated its status by saying it was secured.

The SEC has opened an inquiry into Musk's tweets, according to one person with direct knowledge of the matter.

Reuters was not immediately able to ascertain if this had escalated into a full-blown investigation on Wednesday.

This source said Tesla's independent board members had hired law firm Paul, Weiss, Rifkind, Wharton & Garrison to help handle the SEC inquiry and other fiduciary duties with respect to a potential deal.