Elon Musk has sold 4.4m shares from his Tesla stock which is valued at roughly $4bn (£3.2bn) and expected to help fund his purchase of Twitter.
This has added to fears from Tesla investors that Musk will be distracted by Twitter and less engaged in running the electric car company, analysts said.
Musk reported the sale in a filing with the Securities and Exchange Commission on Thursday.
The shares were sold over the past few days at prices ranging from $872.02 (£695.85) to $999.13 (£797.29).
The world’s richest man, the CEO of Tesla, said in a tweet he does not plan any further sales of the company’s shares.
Most of the sales took place on Tuesday, when Tesla shares closed down 12 per cent, a huge single-day drop.
Twitter agreed to be acquired by Musk on Monday for 44 billion dollars (£35.1 billion).
It was revealed that Musk would borrow up to $25.5bn (£20.4bn) from a slew of banks to pay for the takeover of Twitter, though the stock sale could fund some of that.
The deal to buy Twitter at $54.20 (£43.25) per share was announced earlier this week and is expected to close sometime this year.
But before the deal is completed, shareholders will have to weigh in and so will regulators in the US and in countries where Twitter does business.
Despite objections from some of Twitter’s own employees and users who worry about Musk’s stance on free speech and what it might mean for harassment and hate speech on the platform, it’s expected there will be few hurdles.
Tesla shares closed on Thursday down slightly at 877.51 dollars (£700.24).
They are down 17 per cent so far this year.