Business Insider reported earlier on Thursday that Musk's SpaceX paid $250,000 in 2018 to settle a sexual harassment claim from an unnamed private jet flight attendant who accused Musk of exposing himself to her.
Shares of the electric carmaker skidded about 9 percent to $646.32 on Friday afternoon amid concerns that the alleged sexual misconduct and Musk's political comments could threaten to damage Tesla's brand and sales.
The article quoted an anonymous person who said she was a friend of the flight attendant. The friend had provided a statement as part of the private settlement process, according to the article.
"I have a challenge to this liar who claims their friend saw me 'exposed' – describe just one thing, anything at all (scars, tattoos, …) that isn’t known by the public. She won’t be able to do so, because it never happened," Musk tweeted.
Reuters was not able to verify the Business Insider account. Musk and SpaceX did not respond to Reuters requests for comment on the Business Insider story or on Musk's tweets.