Sunday TimesIreland editor Mr Liam Clarke and his wife, Ms Kathryn Johnston, have been released on bail from police custody.
The couple had been arrested by detectives investigating the leaking of transcripts of telephone conversations between the British Prime Minister's chief of staff and Sinn Féin's Mr Martin McGuinness.
The transcripts were contained in a new updated biography of Mr McGuinness, which was co-written by the couple.
A Police Service of Northern Ireland spokeswoman today confirmed the pair were released early this morning.
A former Special Branch officer arrested on Wednesday by the investigation team remains in custody.
The three arrests followed publication in the London Timesof the transcripts used in the biography, entitled Martin McGuinness, From Guns to Government.
The transcripts detailed conversations between Mr McGuinness and Mr Tony Blair's chief of staff, Mr Jonathan Powell, as well as with former Northern Ireland Secretary Mo Mowlam. At the time, Mr McGuinness was Education Minister and Ms Mowlam was fighting to hold on to her job in advance of a meeting with Mr Blair in August 1999.
Sinn Féin, which has protested to Downing Street, has accused MI5 of bugging the telephone conversations and compiling the transcripts featuring Mr McGuinness.