A major IRA intelligence-gathering operation concentrated on Stormont and Castlereagh special branch offices has now been smashed, according to the PSNI, the Police Service of Northern Ireland.
The acting deputy chief constable, Mr Alan McQuillan, who was yesterday promoted to his new position, said that the investigation, code-named Operation Hezz, had penetrated right to the core of the IRA.
Police had discovered that the IRA had agents working at Stormont, he added.
"The investigation has taken us into the heart of the IRA," he said yesterday. "We have broken a major intelligence unit within the IRA."
Mr McQuillan said that the investigation of the alleged espionage at Stormont was now being linked to the alleged IRA break-in at the former RUC special branch office at Castlereagh station last St Patrick's night.
A dedicated team of 40 detectives was involved in the investigation.
Det Chief Supt Phil Wright, who is heading the investigation, said that judges, forensic scientists, police officers and military personnel, prison officers and loyalists had to be warned about their own security because the IRA had personal details about them.
He added that police had seized 79 computers, some 1,000 computer disks and 2,500 evidential exhibits. There were 19,000 pages of documentation which had to be examined and assessed.
There were 2,000 statements taken and 5,000 people contacted in the investigation to date. The scale of the operation was "huge", he added.
Moreover, a 3,000-page document was compiled and sent to the Director of Public Prosecutions in relation to an attempt to extradite from New York to Northern Ireland a chef who worked at Castlereagh station and whom police wished to question in relation to the break-in.
Mr McQuillan, in an implicit criticism of the effectiveness of the IRA intelligence operation, said the organisation ran "quite a centralised system".
"Therefore, in a relatively small number of locations we have recovered a very large quantity of information," he added.
He indicated that while the alleged IRA infiltration was on a large scale it did not denote a threat to the IRA ceasefire. "We have no information of an intention to use that intelligence in any offensive way," he said.
Some of the information was gathered "up to 12 months ago".
Asked had the infiltration ceased, Mr McQuillan said police were still assessing all the evidence. "I can't give you an honest answer at this stage; we simply don't know yet."
An assessment team of 15 officers working up to 16 hours a day was also involved in determining the level of any threat against those named in the seized documents, computers and computer discs, according to Det Chief Supt Wright.
Mr McQuillan said that it appeared evident from the documentation that the IRA also had a small number of agents operating at Stormont and that it had attempted to put pressure on some civil servants to work for the organisation.
"We are actively investigating a small number of possible approaches to a small number of people in a small number of offices within government.
"Indeed," he added, "we are very conscious that some people working within government who are decent, honest civil servants may well have been approached and may well have had attempts made to induce them to provide information."
Mr McQuillan rejected some recent claims that the timing of the arrests was designed to damage Sinn Féin and the IRA at a time when the IRA was under pressure, in particular from the British Prime Minister, Mr Tony Blair, to commit itself fully to democracy.
"I would not tolerate, and I know the chief constable would not tolerate, any political interference in operational decisions," Mr McQuillan said.
