NEW YORK (CBS News) -- Facebook said Wednesday that the number of users whose data was swept up by Cambridge Analytica could be as high as 87 million, significantly more than the figure of 50 million that was widely reported at the outset of the data scandal more than two weeks ago.
"We only just finalized our understanding of this situation in the last, I think, couple of days on this," CEO Mark Zuckerberg said during a conference call with reporters Wednesday afternoon. "We didn't put out the 50 million number. That came from other parties."
In a blog post, Facebook's Chief Technology Officer Mike Schroepfer said the company believes data from up to 87 million people was "improperly shared" with Cambridge Analytica, the consulting firm who received data on users and their networks from a researcher who developed an app that captured the information. Facebook banned Cambridge Analytica, the researcher and a former employee from the platform in March.
The announcement comes ahead of Zuckerberg's widely anticipated testimony before Congress next week.
Asked about the discrepancy between Facebook's estimate of the number of users affected and the widely reported figure of 50 million, a spokeswoman for the company said Facebook used "an expansive methodology" to arrive at 87 million.
"This is our best estimate of the number of people who both directly installed the app as well as those whose friends' data may have been accessed," the spokesperson said. "The 50 million number originally reported was an estimate provided by parties other than Facebook. We undertook our own internal review to determine the number of people potentially impacted."
Several days after the scandal broke, Zuckerberg was asked in an interview with the New York Times whether Facebook is "planning to notify the 50 million users whose data was shared with Cambridge Analytica."
"Yes. We're going to tell anyone whose data may have been shared," he replied. "Now, there's a question of whether we have the exact record in our systems today of who your friends were on that day when there was access three and a half or four years ago. So, we're going to be conservative on that and try to tell anyone whose data may have been affected, even if we don't know for certain that they were."
Facebook also said Wednesday that it's working to make additional changes to the platform, including more restrictions on data accessible to developers. Last month, the company changed its privacy settings to make them easier to find, something the company has repeatedly promised to do in numerous policy changes over the course of the past 12 years.