"Twitter deal temporarily on hold pending details supporting calculation that spam/fake accounts do indeed represent less than 5 percent of users," Musk said in a tweet.
Shares of the social media company fell 20 percent in premarket trading. Twitter did not immediately respond to a request for comment.
The company had earlier this month estimated that false or spam accounts represented fewer than 5 percent of its monetizable daily active users during the first quarter.
It also said it faced several risks until the deal with Musk is closed, including whether advertisers would continue to spend on Twitter.
Musk had said that one of his priorities would be to remove "spam bots" from the platform.