Facebook has said almost 45,000 people in Ireland may have had their personal data improperly shared with Cambridge Analytica.
It comes after the social network revealed that a total of more than 87 million people - mostly in the US - may have been affected.
It's claimed an academic violated Facebook's terms by sharing data from a personality test app with Cambridge Analytica, a UK-based political consultancy firm.
In a statement this morning, 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."
Facebook says anyone potentially impacted will be informed.
Cambridge Analytica has insisted the data was deleted when they were informed it may have been improperly shared, and said none of the data was used during its work for Donald Trump's campaign during the US presidential election.
Cambridge Analytica licensed data from GSR for 30 million individuals, not 87 million. We did not receive more than 30 million records from research company GSR.
— Cambridge Analytica (@CamAnalytica) April 4, 2018
Facebook CEO Mark Zuckerberg, meanwhile, has admitted his company made mistakes.
He said: "It’s clear now that we didn’t do enough. We didn’t focus enough on preventing abuse and thinking through how people could use these tools to do harm as well.
"That goes for fake news, foreign interference in elections, hate speech, in addition to developers and data privacy."