Elon Musk has said his $44bn (£35bn) deal to buy Twitter is temporarily on hold after he queried the number of fake or spam accounts on the social media platform.
He said he was waiting for information "supporting [the] calculation that spam/fake accounts do indeed represent less than 5% of users".
Following the announcement, Twitter shares fell 25% in pre-market trading.
Mr Musk has been vocal on cleaning up spam accounts.
Twitter reported nearly two weeks ago that fake accounts accounted for less than 5% of its daily active users during the first three months of this year.
However, the company said in determining the amount of spam accounts, "it applied significant judgment, so our estimation of false or spam accounts may not accurately represent the actual number of such accounts".
"The actual number of false or spam accounts could be higher than we have estimated. We are continually seeking to improve our ability to estimate the total number of spam accounts," it said.
Mr Musk, who is the richest person in the world according to Forbes magazine, is now examining that figure.
Under the terms of the deal, if either Twitter or Mr Musk walk away they must pay the other side a termination fee of $1bn.