Days after Elon Musk made headlines for repeating unsubstantiated allegations that a British diver involved in the Thailand cave rescue is a pedophile, the CEO of Tesla and SpaceX provoked more investor uncertainty when he appeared to smoke a blunt on-air during a podcast.

Shares of Tesla fell more than 6 per cent to reach a five-month low on Friday morning following the departure of the company’s chief accounting officer, Dave Morton, who resigned less than a month into the job on Friday.

The two-and-a-half hour conversation with host Joe Rogan on “The Joe Rogan Experience,” which aired Thursday evening, covered everything from artificial intelligence to samurai swords. At one point, Musk took a brief pull on a blunt Rogan said contained cannabis and tobacco.

“I mean it’s legal, right?” Musk asked Rogan to which he responded, “Totally legal.”

The 47-year-old billionaire later said he wasn’t a “regular smoker” of marijuana because he doesn’t find it “very good for productivity.”

Musk’s behaviour has created concern among Tesla shareholders who have questioned his leadership ability following a series of controversies in recent months.

In July, Musk raised eyebrows when he accused British diver Vern Unsworth – who aided in the rescue of 12 boys and their coach in Thailand cave this summer – of being a “pedo” or pedophile in a tweet. He provided no evidence to support his claim. Following intense backlash, Musk apologized to Unsworth a few days later.

That apology appeared to be disingenuous, however, because on Wednesday, Musk repeated his earlier allegations in an interview with BuzzFeed News. In an email exchange, he told the news outlet that Unsworth was a “child rapist.” Again, he didn’t offer any evidence to back up the accusations. Unsworth has denied Musk’s allegations.

A month later, Musk was the centre of attention again when he tweeted that he had secured enough funding to take his electric-car company Tesla private for $420 per share. The surprising announcement sent the stock soaring and then plummeting when doubts were raised about his plan’s feasibility.

Soon after, Musk changed his mind and said he decided the company would remain public. The about-face attracted attention from the U.S. Securities and Exchange Commission, which reportedly launched an investigation into Tesla for possible stock manipulation. Musk has said he stands by his initial tweet about the company going private.

The billionaire entrepreneur addressed his tumultuous year in an emotional interview with The New York Times in August, in which he admitted he was experiencing the “most difficult and painful year” of his career.

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