An inquiry into alleged Garda collusion with the IRA in the murder of two senior RUC officers is expected to seek a third extension.
Legal sources said the chairman of the Smithwick Tribunal will have no choice but to apply to the Government for more time to deal with "explosive" new evidence that emerged last week.
The Police Service Northern Ireland (PSNI) produced never-before-seen evidence last Wednesday, as the probe into the IRA killing of Chief Superintendent Harry Breen and Superintendent Bob Buchanan in Dundalk in 1989 entered its final stages.
The five documents included claims an officer told colleagues he was worried three men were sharing information with the IRA.
The inquiry, chaired by Judge Peter Smithwick, has focused on former garda officers Owen Corrigan, Leo Colton and Finbarr Hickey, who deny passing information.
After the new material emerged last Wednesday, the Buchanan family called for a new cross-border investigation into the murders.
They claimed the new evidence included in the five documents pointed to collusion between members of the gardai and the IRA. They also criticised the PSNI for withholding the information, which is understood to have come to light in the last eight years.
As Judge Peter Smithwick earlier adjourned the tribunal until the end of August, Mr Corrigan's solicitor said he had not finished cross-examining his client. He, and possibly others implicated with the new evidence, are expected to return to the witness box in the autumn.
The tribunal was established in 2005 when Canadian judge, Peter Cory, recommended a public inquiry be held in to allegations of collusion by garda officers, or a civilian in the force. It opened nearly a year later and was adjourned almost immediately to allow for private investigations. Public hearings started in June last year.
It has sat for more than 120 days, heard evidence from 200 plus witnesses, and cost well over 8 million euro to date.