The RUC Chief Constable and Northern Ireland Secretary have both welcomed the decision of the Northern Ireland Ombudsman to investigate claims that the RUC had foreknowledge about the Omagh bombing.
Sir Ronnie Flanagan said the claim by a former British army informant who was a member of the Irish National Liberation Army (INLA) and IRA was "preposterous".
Senior security sources have told The Irish Times that both the Garda and RUC were aware that the "Real IRA" had moved a substantial amount of explosives from a village in Co Meath to the Border area north of Dundalk about two weeks before the Omagh explosion.
The "Real IRA" carried out a test detonation with about half the explosive.
While the Garda and RUC were both aware that explosives had been moved into the south Armagh area and that a bomb was almost certainly being made, neither force was aware that the "Real IRA`' intended to carry out a bombing in Omagh, the sources said.
The Chief Constable said it was entirely right that the Ombudsman was investigating the claim as it could assuage some of the trauma suffered by the families of the 29 people killed in the bombing on August 15th, 1998.
Dr Reid also welcomed the investigation and hoped it would find that the allegations were baseless.
There was an angry unionist reaction to the news and one call for the resignation of the Ombudsman, Ms Nuala O'Loan.
Ms O'Loan responded: "It would not be in the interests of either the public, or the police, for such specific and damaging allegations to be ignored."
The former Ulster Unionist MP, Lord Maginnis, called for Ms O'Loan to resign.
He said: "She is moving into an area that is so complex that it illustrates her lack of understanding."
The former agent, who uses the pseudonym Kevin Fulton and who comes from Newry, will be interviewed by officials working for the Ombudsman.
Former Det Chief Supt Eric Anderson, who headed the RUC investigation, as well as some of his senior officers on the case, are also expected to be interviewed.