The Northern Ireland editor of the Sunday Times, Liam Clarke, was last night released without charge by the Police Service of Northern Ireland (PSNI).
Mr Clarke's wife, Ms Kathryn Johnston, was also released.
The couple were detained for questioning on Thursday by police investigating leaked transcripts of telephone calls made by the deputy leader of Sinn Féin, Mr Martin McGuinness.
The calls, purportedly taped by MI5, are to be published in a a biography of Mr McGuinness written by Clarke and Ms Johnson.
A third man was last night charged as part of the same investigation. Details of the transcripts were reported in the Irish News in Belfast and the Times in London earlier in the week.
The transcripts are of telephone conversations between Mr McGuinness and former Northern Ireland Secretary, Ms Mo Mowlam, and Mr Tony Blair's chief of staff, Mr Jonathan Powell. Documents were also seized when Clarke and his wife were arrested.
A PSNI spokesman last night said the couple had been released pending further inquiries.
A 48-year-old former policeman who had been detained in connection with the same police investigation was last night charged with offences under the official secrets act, according to the PSNI.
The man had been released last night but will appear in court at a later date.
