As Facebook deals with the fallout from a scandal involving misused data from 50 million user accounts, the social network said it’s getting outside help to investigate the matter.

The company on Monday said it’s hired the digital forensics firm Stroz Friedberg to conduct a comprehensive audit of Cambridge Analytica, a consultancy used by the Trump campaign that received the data from a third-party app developer.

Over the weekend, The New York Times and the Guardian reported that the data initially came from Cambridge professor Aleksandr Kogan, who created the app “thisisyourdigitallife,” a personality quiz that was billed as “a research app used by psychologists.”

Kogan legitimately gained access to information on 270,000 accounts through Facebook’s Login feature, but then broke the social network’s rules with app developers by passing the data onto Cambridge Analytica. Chris Wylie, who worked for the consultancy, is the whistleblower who took the story to the press.

Facebook found out about the violation in 2015 and demanded all parties involved destroy the data. But now there are allegations not all of the data was deleted.

“We are moving aggressively to determine the accuracy of these claims,” Facebook said in a blog post. “We remain committed to vigorously enforcing our policies to protect people’s information.”

Facebook said Cambridge Analytica has given the forensics firm complete access to its servers and systems. The social network also said it asked Kogan and Wylie to submit their own audits. Kogan has agreed but Wylie declined, Facebook said.

At the time Kogan allegedly collected the information, Facebook allowed developers to also access information not only from the people who opted into the feature, but some other data about their network of friends. That added up to info from 50 million accounts, according to the Times. (Facebook changed its rules three years ago to stop developers from seeing information about people’s friends.)

“Kogan’s app would not be permitted access to detailed friends’ data today,” Facebook said.

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