The stock lost 6 percent by midday trading Thursday, falling below $346 before paring some losses to close at $352.45. That erases all gains prompted by a tweet on Tuesday in which Musk publicly floated the possibility of going private, sending shares up 11 percent.
The stock was down most of the day, and dipped more after a Bloomberg report that the SEC had been gathering information on Tesla prior to Tuesday. The agency had been looking into Tesla's public statements on production numbers and sales targets, the news site reported, and intensified its scrutiny after Tuesday's tweet.
With Thursday's dip, Tesla stock is up 13 percent in 2018 but flirting with correction territory, nearly 10 percent off its 52-week high.
Correction: This article has been revised to clarify that the Bloomberg report said the SEC had been gathering information on Tesla before Tuesday.