The Data Protection Commissioner intends to investigate whether personal data was accessed in an alleged data breach at Independent News & Media.
In a statement, Commissioner Helen Dixon added that she would be investigating whether data was it processed in accordance with data protection legislation.
The statement added that the Commissioner is currently establishing the parameters of the investigation, including seeking additional information from INM on foot of the breach notification it filed with the office last week.
The Editor-in-Chief of INM has told staff their welfare is the company's primary concern, following the allegations of a significant data breach.
Stephen Rae told staff that individuals from the company who had been named as having their emails searched had been informed.
He said: "Clearly we have to get to the bottom of what is alleged to have occurred and as always identify the actual facts of the case in the first instance and thereafter what lessons can be learned."
The development comes as the Director of Corporate Enforcement, Ian Drennan, has prepared an affidavit for a High Court case in advance of his request to have inspectors appointed to INM.
The court case is due to be heard on 16 April.
Mr Drennan's affidavit alleges there was a significant data breach and information related to 19 individuals was accessed on INM's system in 2014.
Among them is Brendan O'Connor, Deputy Editor of the Sunday Independent and presenter of the Cutting Edge on RTÉ One.
Also named is Sunday Independent investigative journalist Maeve Sheehan and journalist Sam Smyth, who previously worked with the Irish Independent.
Also on the list are INM's former director of corporate affairs Karl Brophy, the former CEO Vincent Crowley, former finance director Donal Buggy, and former CEO of the company's Irish division Joe Webb.
The names have been reported in the Irish Independent today.
Also listed are two barristers, Jacqueline O'Brien and Jerry Healy, both of whom had been engaged by the Moriarty Tribunal.
Mr Drennan has alleged data was removed from the jurisdiction and interrogated.
The National Union of Journalists has welcomed the announcement of an investigation.
Speaking on RTÉ's News at One programme earlier, NUJ secretary Seamus Dooley called for an "immediate investigation" by the Data Protection Commissioner.
"This stinks to high heavens. It's not an exaggeration to say that this is our Leveson moment," he said, referring to the British inquiry following revelations around phone hacking by journalists.
"Journalists are obliged to protect confidential sources of information and of course normally when we associate protecting sources, we identify the threat as being external," he said. "What is alleged here is that the threat came internally, and that makes it all the more serious."
Also speaking on the News at One, journalist Sam Smyth said he first learned that his communications may have been searched a week ago, after a friend of his told him that he had appeared on a list of names relating to the breach.
He said that he has yet to be contacted by INM in relation to the matter.
"I heard nothing whatsoever from INM or anybody else in authority there, the first time I saw it confirmed was this morning when it was in the Irish Independent," he said. "When I read it in the Irish Independent I took it seriously because it's INM that's in the firestorm of this, so you'd assume if anybody had knowledge of it, it would be them."
Mr Smyth said he is no entirely surprised by the claims as "for a long time rumours were flying", while he had previously been urged by security professionals to be careful in how he was communicating.
"There was an air almost of inevitability about it, because we've spoken about this for some time," he said.
Mr Smyth also said that he would now take advice from legal professionals about the matter.