LONDON: Britain is investigating whether Facebook did enough to secure data after reports that a political consultancy hired by Donald Trump improperly accessed information about 50 million Facebook users, Information Commissioner Elizabeth Denham said on Tuesday. Denham is seeking a warrant to search the offices of London-based consultancy Cambridge Analytica after a whistleblower revealed it had harvested the private information of millions of people to support Trump's 2016 US presidential campaign. Facebook shares closed down nearly 7 percent on Monday, wiping nearly $40 billion off its market value as investors worried that new legislation could damage the company's advertising business and hurt its appeal to users. The investigations of Cambridge Analytica and Facebook were part of a wider probe into the use of personal data, said Denham, whose office is tasked with enforcing Britain's data protection laws. 'We are looking at whether or not Facebook secured and safeguarded personal information on the platform and whether when they found out about the loss of the data they acted robustly and whether or not people were informed,' she told BBC Radio. Denham said she would investigate whether Facebook had met its data protection obligations. Cambridge Analytica denies media reports that it misused data, and says it deleted all Facebook data obtained from a third-party application in 2014 after learning the information did not adhere to data protection rules.