RUC Special Branch carried out around 200 suspect interviews in the days after the La Mon bombing that claimed the lives of 12 people.
Three married couples were among the dead when the firebomb ripped through the hotel on the outskirts of east Belfast in February 1978, which also resulted in 30 people being injured.
The attack was later claimed by the IRA.
Those who died were attending an Irish Collie Club event when the bomb went off outside a function room.
A Police Ombudsman report published on Wednesday revealed that “collusive behaviours were not a feature of the RUC investigation of the bombing”.
It also confirms that the ombudsman found no evidence that anyone involved in the attack was “protected”.
“This investigation identified no intelligence that, if acted upon, could have forewarned of, or prevented, the bombing,” it also states.
It has now emerged that in the days after the attack, between February 18–24, 35 people were arrested as part of a “disruptive lift” designed to “disrupt the activities of PIRA”.
Of around 300 police interviews carried out between February 18-28, two-thirds, or 200, were undertaken by RUC Special Branch.
The report sets out that while initial interviews were generally carried out by CID officers there were times that Special Branch were the only officers to carry out the task.
The report says “the limited number of surviving interview notes” reflect that were Special Branch “were deployed to the investigation to augment the available CID resources”.
The report, which runs to more than 130 pages, confirmed that seven suspects, each attributed a cipher A-G, believed to have been involved have been identified.
Two of those, referred to Person A and Person B in the report, were later prosecuted.
Person B was convicted of 12 counts of manslaughter in 1981 and Person A acquitted during his trial in 1980.
At the time, a judge said he could not be satisfied beyond reasonable doubt that statements made by the man had not been “adduced by torture or inhuman or degrading treatment” by the RUC.
It has emerged that Person A was arrested on February 18, 1978, and released without charge.
He was again detained in September 1978 and admitted to being a member of the IRA and supplying the La Mon bomb.
He claimed that when asked for a bomb a day before the La Mon attack by a member of the IRA, he refused “as it was required for another attack”.
He was later told to go to an address in west Belfast where he was told by Person G, described as ‘high up’ in the IRA, “to provide a bomb that would be used at La Mon House or he would be shot”.
He later handed the bomb over.
During interview, he told police it was ‘his team’ that had carried out the attack, although he denied being present.
Elsewhere in the report it states that in late February 1978 “the RUC received intelligence identifying PIRA Belfast as having carried out the bombing at La Mon House”.
“Also in late February 1978, intelligence stated that the bombing at La Mon House had not been directed or sanctioned by Belfast PIRA leadership.”
The report adds that intelligence suggested the IRA’s 1st battalion, which covers west Belfast, “carried out the attack without first seeking permission from their higher leadership structure”.
Under a section headed ‘post-incident intelligence’, it is claimed one person arrested, who was “suspected to be a senior member of PIRA speculated to police that elements of the British State may have been responsible for the bombing in order to ‘stir things up’ between the Protestant and Catholic communities”.
The ombudsman’s report highlighted that some records and exhibits from the original investigation had been lost over the years.
Investigators found that some enquiries appeared not to have been carried out by the RUC.
It has also emerged that investigators have retained DNA linked to the IRA bomb.
A sample was found on adhesive tape found on the remnants of the device after it exploded.
According to the report the now defunct Historical Enquiries Team reported that it asked for tests to be carried out and when analysed “no profile was obtained due to an insufficient quantity of DNA”.
Andrea Nelson, who was 14 when her parents Paul and Dorothy, were killed was satisfied with the ombudsman’s report.
“From what I have seen so far this has been a diligently undertaken piece of work that has found no evidence of collusion or paths to preventing La Mon, which was very important to hear for the families,” she told The Irish News.
“And there’s no evidence that the investigation was impeded in any way by persons seeking to protect informants and they also acknowledge that the family liaison practices of 40 years ago are not what is deemed to be good practice these days.”
Ms Nelson said she intends to read the report “in detail”.
“We are given some hope in terms of the DNA evidence that is still held by the forensic service and which the advances in DNA typing over the last decade or so may result in there being a profile retrieved from that DNA,” she said.
Paul Holmes, Senior Director of Investigations at the Police Ombudsman, said he could ‘neither confirm nor deny’ when asked if there was any indication of the involvement of a state agent at the time or someone who subsequently became a state agent.
“We haven’t identified any malpractice or suspicion of malpractice in relation to the handling of any informant when it comes to the La Mon House bombing,” he added.
Mr Holmes said he concluded there “was earnest endeavour by the RUC to bring those responsible for the bombing of La Mon House to justice”.
Assistant Chief Constable Ryan Henderson, said: “While the Police Ombudsman’s report has identified some investigative failings it also highlights that the investigation was well resourced, comprehensive and effective.
“The report has found that police held no intelligence prior to the attack that could have prevented it and also found that there was no evidence that any persons were protected from prosecution.”
