American billionaire Elon Musk has temporarily put on hold his deal to buy Twitter Inc for $44 billion, Reuters reports.

Shares of the social media company fell 17.7% to $37.10 in premarket trading, the lowest level since Musk disclosed his stake in the company in early April and subsequently made a best and final offer to make it private at a price of $54.20 per share.

Twitter earlier this month estimated that fake or spam accounts accounted for less than 5% of its monetized daily active users during the first quarter, when it registered 229 million users who were shown ads.

Twitter deal is on hold pending details supporting calculations that spam/fake accounts do indeed account for less than 5% of users, Musk tweeted Friday.

The social media company said it faces a number of risks until the Musk deal closes, including whether advertisers will continue to spend money on Twitter amid potential uncertainty about future plans and strategy.