Mark Zuckerberg, founder and chief executive officer of Facebook, speaks during the APEC 2016 CEO Summit in Lima, Peru, on November 19, 2016.

Australia's Privacy Commissioner said on Thursday she had opened a formal investigation into social media giant Facebook after the company confirmed data from 300,000 Australian users may have been used without authorization.

The investigation will consider whether Facebook has breached Australia's privacy laws, Privacy Commissioner Angelene Falk said in a statement.

Facebook said on Wednesday that the personal information of up to 87 million users, mostly in the United States, may have been improperly shared with political consultancy Cambridge Analytica, up from a previous news media estimate of more than 50 million.