A book detailing terrorist threats vanished from Omagh police station at the height of inquiries into the RUC investigation of the bomb atrocity, it was revealed tonight.
It disappeared after senior officers were questioned about warnings in advance of the Real IRA attack which left 29 people dead.
The book recorded details of threatened terrorist strikes passed on to the RUC in Omagh. But it was reported missing as attempts were made to establish the sequence of events and level of contact between Special Branch, CID and uniformed officers in the run-up to the August l998 bombing.
Eleven days before the car bombing, police in Omagh were tipped off that terrorists were planning to attack security forces in the town. The warning was not passed on to senior commanders.
The book's mysterious disappearance has never been explained, but it meant that officers from Ombudsman Ms Nuala O'Loan's office, who conducted an inquiry into the police investigation, were unable to examine a hugely important record which documented threats, their significance, and the type of action, if any, taken at the time.
The book's loss was confirmed in her full report to Northern Ireland Secretary Dr John Reid, Chief Constable Sir Ronnie Flanagan and the new policing board - but not in the summary which was handed over to the victims' relatives last month.
A spokesman for the Ombudsman said: "There are a number of issues in the full report which it was not felt appropriate should be made public at that stage."
It is understood the hardback book had been kept in the top of drawer of a senior officer's desk at the Omagh police station. The O'Loan investigating team of officers asked to see it in September last year, but were told it had gone missing.
Sources said they believed it vanished in August 2000 when the RUC was carrying out its own review of the inquiry.
Mr Michael Gallagher, whose son Aidan, 21, was among the dead, said he was flabbergasted: "What are they [the police] playing at? What is going on?"
"It seems extraordinary that a book of this importance can disappear in a controlled environment of a police station."
Mr Martin Bridger, the deputy director of investigations at the Ombudsman's office, is having a meeting with relatives in Omagh later tonight. He refused to comment about the missing book.
But the Chief Constable can expect to be questioned about it when he meets with relatives on Thursday when he delivers his response to the stinging criticism of his leadership over Omagh by the Ombudsman.
On August 4th, l998, the RUC Special Branch was tipped off about a planned attack by republican dissidents on police in Omagh 11 days later - the day on which the Real IRA car bomb exploded in the town's Market St.
But the information was not passed on to senior commanders on the ground and therefore would not have been contained in the threat book.
The O'Loan investigation team wanted to examine it to find out how many threats had been recorded previously, to assess their importance and to study what action, if any, had been ordered as a response.
Police tonight refused to comment on the loss of the book.
PA