The IRA is understood to be searching for a former leading Armagh member suspected of having defected to the dissident Continuity IRA. This man may also have led the gang involved in last week's bombing in Markethill, Co Armagh.
It appears that the Markethill bomb contained relatively up-to-date IRA detonating apparatus. This would suggest that equipment was stolen from an IRA bomb dump.
Previous bombs manufactured by the Continuity IRA contained detonating apparatus which was copied from IRA bombs of the early 1980s.
The man suspected of leading the attack is a member of a well-known republican family which includes figures killed in active service with the IRA.
He is the most high-profile republican paramilitary figure known to have defected to the dissident group.
His defection and the apparent theft of equipment for use by the Continuity IRA has presented the IRA leadership with a problem as its political wing, Sinn Fein, engages in political talks at Stormont.
The IRA's General Order No 11, which deals with the seizure of arms and arms dumps, states that the only punishment for any member who steals equipment or explosives is death.
But taking this course would place the IRA clearly outside the Mitchell Principles of non-violence which govern access to the talks process at Stormont and might affect Sinn Fein's participation.
The search for the dissident Armagh IRA figure comes after reports from Belfast that an attack by another Continuity IRA figure in the republican Ardoyne area was thwarted when local armed IRA men surrounded and disarmed a man carrying a rifle. Republican sources say this incident took place within days of the Markethill bombing.
The bombing has raised considerable concerns about the Continuity IRA, which was previously thought to have only a few dozen members with basic bomb-making skills.
The explosion caused widespread damage in the market square in front of the local RUC station but caused almost no damage to the station itself as it is protected by a blast wall. This was erected after the original station was destroyed in another IRA blast in 1991.
The Ford Transit van used in the attack was stolen in Dundalk in early September and it would seem the bomb was loaded on board somewhere in the Louth-Monaghan-Armagh area.
This is territory which the IRA has traditionally regarded as one of its strongholds. Dissent in this area, particularly from a family with a republican pedigree, will be a major source of concern within the IRA.