More than 44,000 people in Ireland may have had their data improperly shared with Cambridge Analytica, the social network has said.
It comes as Facebook CEO Mark Zuckerberg has admitted the company "didn't do enough" to prevent abuse of its platform.
Yesterday the company revealed more than 87 million people around the world may have had their data improperly shared with Cambridge Analytica - significantly more than earlier estimates of 50 million.
Facebook had previously accused an academic, Dr Aleksandr Kogan, of violating its terms by passing on data from a personality test app - thisisyourdigitallife - to the UK-based political consultancy firm.
According to the social network, the vast majority of accounts - 70 million - that may have been affected belong to people in the US.
In a statement to Newstalk, Facebook said: "Our investigation shows that the people impacted were predominantly in the United States – 97.1% of users who installed the app are understood to have been primarily in the US, while 81.2% of total affected people.
"However, we do know that 15 people in Ireland installed thisisyourdigitallife, and up to 44,687 people in Ireland may have been friends with someone who installed the app, and, therefore, may have been affected."
Anyone potentially affected will be informed, Facebook has said.
The revelations last month prompted a number of international investigations, with Facebook this week confirming Mr Zuckerberg will testify before Congress over the controversy.
Cambridge Analytica - which is known for its work for political groups, including Donald Trump's presidential claim - has said it did not receive data from 87 million people, and insisted it immediately deleted data when it was informed data may have been improperly obtained.
It also says none of the data was used during the 2016 US election.
