NEW YORK: Billionaire Elon Musk was sued by Twitter Inc investors for delayed disclosure of his stake in the company, as the owner of electric carmaker Tesla Inc mounts a $44 billion takeover bid for the social media platform.

The investors said Musk saved himself $156 million by failing to disclose that he had purchased more than 5% of Twitter by March 14.

He continued to buy stock after that, and ultimately disclosed in early April that he owned 9.2% of the company, according to the lawsuit, filed on Wednesday in San Francisco federal court.

“By delaying his disclosure of his stake in Twitter, Musk engaged in market manipulation and bought Twitter stock at an artificially low price,” said the investors, led by Virginia resident William Heresniak.

Neither Musk nor his lawyer immediately responded to requests for comment. Twitter declined to comment.

The investors said the recent drop in Tesla’s stock has put Musk’s ability to finance his acquisition of Twitter in “major peril” since he has pledged his shares as collateral to secure the loans he needs to buy the company.

Tesla’s shares were trading around $700 on Thursday, down from above $1,000 in early April.

The timing of Musk’s disclosure of his stake has already triggered an investigation by the US Securities and Exchange Commission (SEC), the Wall Street Journal reported earlier this month.

Musk on Wednesday pledged an additional $6.25 billion in equity financing to fund his bid for Twitter, a sign he is working to complete the deal even though he last week conditioned its progress on Twitter presenting proof that spam bots accounted for less than 5% of its users.

In Wednesday’s suit, the investors asked to be certified as a class and to be awarded an unspecified amount of punitive and compensatory damages.