Image copyright Getty Images Image caption Lawmakers are hoping to return Mark Zuckerberg to the Congressional hot seat
Facebook has assured US lawmakers that it will protect the accounts of all 12 million users whose data was compromised by Cambridge Analytica.
CEO Mark Zuckerberg is expected to return to Capitol Hill for a second hearing over the firm’s handling of the incident.
He will also face tough questions about data handling practices and the impact of misleading political advertising.
In April, Mr Zuckerberg declined a request to answer questions from members of the committee.
‘He spoke. That’s what they wanted’
He told US lawmakers in April that he had already testified publicly about the issue and other major internet companies were also being called to explain their data practices.
The story was first reported by the Observer newspaper in the UK, and later covered by the New York Times.
Users whose data had been accessed included millions of voters in the US states of Michigan and Wisconsin and the Democratic data analytics firm 270 Strategies, a company that has worked for Democratic presidential nominee Hillary Clinton.
Mr Zuckerberg will be grilled again on the issue on Wednesday by members of the House Energy and Commerce Committee.
Analysis by Simon Owen, BBC technology correspondent
It will be another close brush with the US legislators, who have been increasingly livid over what many see as their porous data-protection laws.
While many American privacy laws have been tightened in recent years, there are still significant differences with those in the UK and Europe, such as the right to quick access to personal data held by American technology firms.
To put this in perspective, US users can ask Facebook to give them the same data on a public figure or an advertiser that they might get in the UK, but it’s not really their right.
Facebook is also standing firmly behind the company it hired to stop the leak in early 2016.
Dr Aleksandr Kogan, the man behind the data analytics firm Cambridge Analytica, who commissioned the data to be harvested, pleaded guilty in April to one count of “criminal contempt of court”.
It remains unclear how Kogan or Cambridge Analytica might profit from the improperly stored data.
Facebook has said that it is not working with prosecutors to investigate Kogan, although it may be willing to be called by Congress.
Amid increasing demands from US lawmakers, UK lawmakers are also investigating how Britain’s Information Commissioner’s Office obtained a warrant to visit Cambridge Analytica’s offices.
Facebook has continued to face calls to extend its policy of user notification to allow for the deletion of the account of anyone who was accessed by Cambridge Analytica in breach of the social network’s rules.
After a backlash following the Cambridge Analytica episode, Mr Zuckerberg announced a two-part feature this year, but it remains unclear what effect it has had.
Lawmakers will also ask Mr Zuckerberg about a new feature that is designed to prevent users from stealing another person’s Facebook data.
In another notable announcement in early June, Facebook announced it would be opening an office in Menlo Park, California.
The firm had already a in other locations in the Silicon Valley, where many large tech firms are based.
Mr Zuckerberg’s UK-based companies – Facebook, WhatsApp and Instagram – are also expanding in London.