The data company that worked for Donald Trump's 2016 presidential election campaign has been suspended by Facebook for allegedly flouting data privacy policies.
The social media giant said it had received reports that Cambridge Analytica did not delete information about Facebook users that had been inappropriately shared.
According to Facebook, University of Cambridge professor Aleksandr Kogan made a personality app that gathered data which he then sold on to third parties.
Cambridge Analytica provided data on the thoughts of American voters to Mr Trump's political campaign strategists and played a role in the Brexit referendum.
In a blog, Facebook's legal counsel Paul Grewal said: "In 2015 we learned that a psychology professor at the University of Cambridge named Dr Aleksandr Kogan violated our platform policies.
"Like all developers, Kogan requested and gained access to information from people after they chose to download his app. His app, 'thisisyourdigitallife' offered a personality prediction and billed itself on Facebook as a 'research app used by psychologists'.
"Approximately 270,000 people downloaded the app. In doing so they gave their consent for Kogan to access information such as the city they set on their profile, or content they had liked as well as more limited information about friends who had their privacy settings set to allow it.
"Although Kogan gained access to this information in a legitimate way and through the proper channels that governed all developers on Facebook at that time, he did not subsequently abide by our rules."
Mr Grewal said that by passing information on to a third party, including Cambridge Analytical and Christopher Wylie of Eunoia Technologies, he "violated our platform policies".
"When we learned of this violation in 2015, we removed his app from Facebook and demanded certifications from Kogan and all parties he had given data to that the information had been destroyed. Cambridge Analytica, Kogan and Wylie all certified to us that they destroyed the data.
"Several days ago, we received reports that, contrary to the certifications we were given, not all data was deleted. We are moving aggressively to determine the accuracy of these claims.
"If true, this is another unacceptable violation of trust and the commitments they made. We are suspending SCL/Cambridge Analytica, Wylie and Kogan from Facebook, pending further information."
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He added that legal action over the alleged violations may follow.
Neither Cambridge Analytica nor professor Kogan have commented on the Facebook decision.