The Continuity IRA, which is suspected of carrying out last night's attacks on hotels in Co Fermanagh, is known to have been attempting to organise a bombing in the North since last summer.
There was a security alert on both sides of the Border at the end of the summer after gardai learned that a car bomb had been constructed in the Republic.
A number of raids on the homes of suspected dissident republicans in the west of Ireland took place as part of an operation to track the bomb. However, nothing was found.
It is believed the bomb was constructed in the mid-west and was then moved northwards close to the Border. At this point it disappeared. This may have been the bomb which exploded at Irvinestown last night.
The group calling itself the Continuity IRA is thought most likely to be behind the bomb plot. This group is the paramilitary wing of Republican Sinn Fein, the party which broke from Sinn Fein in 1986.
The Continuity IRA has existed since about 1991 and has carried out several attacks in the North, but has never killed anyone. However, members of the group have close links with the "Real IRA", the group responsible for the Omagh bombing.
The Continuity IRA is known to have become active since the start of last year, mounting ineffective attacks on security targets in Northern Ireland. Some of its members have been arrested there.
Gardai have also detected a rise of activity among the group's members in the Republic. The group has a national organiser, a Cork man who may be living in the midlands. He is reported to have been very active over the past year. It is believed he may have put together a bomb-making team, possibly with a base in Roscommon.
Gardai from the Crime and Security Branch at Garda headquarters have closely watched the group's activities, and last month intercepted an attempt to move home-made missiles into Northern Ireland. These had been taken from Provisional IRA arms dumps.
The main concern among senior gardai is that there may be a strategic alliance forming between the Continuity IRA, based mostly in the west, and the south Armagh/Dundalk-based "Real IRA".
The "Real IRA" mounted bomb attacks in the North in 1997 and 1998 in an unsuccessful attempt to damage the political talks at key moments in the process. "Real IRA" bombers were twice intercepted by gardai as they tried to mount attacks in the days before the signing of the Belfast Agreement.
After the Omagh bombing, the "Real IRA" disintegrated in the face of adverse public opinion and a major Garda investigation. It called a ceasefire, but the Continuity IRA refused to do so.
As part of the Omagh investigation, gardai discovered there was dual membership between the two groups, which were sharing expertise and personnel. It would appear that the Continuity IRA is now leading republican dissent against the Provisional IRA ceasefire.
Garda sources also report there has been an increase in Provisional IRA activity, and suspect the group may have been involved in firearms training in the Slieve Bloom area in the past month. However, sources say there is no indication that the Provisional IRA is about to break its ceasefire.
During 1995 the Continuity IRA twice attacked Protestant-owned hotels in Co Fermanagh. Continuity IRA bombers also damaged an Enniskillen disco in 1997.