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 campaign - 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.
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
Separately, Facebook also suggested "most people on Facebook could have had their public profile scraped" by "malicious actors" using phone numbers and email addresses to search for profile information.
The company confirmed they have disabled that search feature, adding: "We’re also making changes to account recovery to reduce the risk of scraping as well".
In a call with reporters yesterday, Mr Zuckerberg 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.
"We didn’t take a broad enough view of what our responsibility is, and that was a huge mistake. It was my mistake."
Speaking about the updated number of accounts, he observed: "We didn’t put out the 50 million number. That came from other parties. We wanted to wait until we had the full understanding. Just to give you the complete picture on this: we don’t have logs going back from when exactly [Aleksandr] Kogan’s app queried for everyone’s friends.
"What we did was basically constructed the maximum possible number of friends lists that everyone could have had over the time, and assumed that Kogan queried each person at the time when they had the maximum number of connections that would’ve been available to them."
He added: "We wanted to take a broad view that is a conservative estimate. I am quite confident that given our analysis that it is not more than 87 million. It very well could be less, but we wanted to put out the maximum we felt that it could be as that analysis says."
Mr Zuckerberg also indicated he will not be stepping down.
He told reporters nobody had been fired over the data controversy, noting: "I started this place. I run it. And I am responsible for what happens here.
"I still think that I’m going to do the best job to help run it going forward. I’m not looking to throw anyone else under the bus for mistakes that we’ve made here."
Facebook has introduced a batch of new measures in response to the scandal - ranging from improved privacy tools for users, to significant changes to the data app developers are able to access.