Gardai have demanded that three journalists with the Evening Herald newspaper hand themselves in for questioning.
It follows the newspaper publishing a leaked letter which led to the resignation of Trevor Sargent as a junior minister.
Last week's Herald story revealed how the former Green Party leader Trevor Sargent lobbied gardaí involved in a criminal investigation.
Hours later Deputy Sargent stepped down as Minister of State at the Department of Agriculture.
Today the Herald is reporting that a top garda from the National Bureau of criminal Investigation has written to the paper demanding the documents that led to the story's publication.
Gardaí also want the three journalists behind the story to make themselves available for interview.
In response the paper's lawyer has claimed that the investigation into the leak shows a lack of clarity and is politically motivated.