BERLIN, April 10 (Reuters) - Facebook has responded to a request for information from a German privacy official on the leak of personal data of millions of users, meeting a deadline that fell just as CEO Mark Zuckerberg prepares to testify before the U.S. Congress.
Johannes Caspar, the regulator for the city-state of Hamburg where Facebook has its German office, sought answers after news broke last month that the data may have been passed to political consultancy Cambridge Analytica without users' knowledge.
A spokesman for Caspar confirmed that Facebook had sent in its submission on Monday, before a midnight deadline, and said that his review would probably be completed by next week at the earliest.
A Facebook spokesman said: "We remain strongly committed to protecting people's information. We appreciate any opportunity to answer questions the data protection authorities may have."
Facebook, the world's largest social network with more than 2 billion users, has said that details of as many as 87 million people, gathered using an online personality quiz, may have been improperly shared with Cambridge Analytica.
While only around 270,000 people actually took the quiz, the app, designed by Cambridge University psychologist Aleksandr Kogan, also gathered information on the participants' 'friends' without their knowledge or consent.
Cambridge Analytica, which advised Donald Trump on his presidential run, has said the data was not used in the 2016 campaign.
Caspar, in his initial reaction, said many users were unaware that Facebook had made their data available to third parties because its terms of service and user interface were so hard to understand.
"This exposure, which for most users has happened completely invisibly via their friends, is alarming," Caspar told Reuters on March 20. He also said he planned to further investigate Facebook's compliance with European Union privacy rules that enter into force next month.
Zuckerberg met U.S. lawmakers on Monday to apologise for Facebook's misuse of its members' data, ahead of two days of congressional hearings in which he is also likely to be grilled about ads and posts placed by Russian operatives. (Reporting by Hans-Edzard Busemann Writing by Douglas Busvine. Editing by Jane Merriman)