Two men arrested over the murder of IRA informer Denis Donaldson remain in custody.
A 31-year-old suspect was detained just hours after a 69-year-old man was held for questioning on Tuesday evening in the Irish Republic.
Both men are being held at Letterkenny Garda station, Co Donegal, under Section 30 of the Offences Against the State Act and can be held for up to 72 hours.
The pensioner, originally from the Dungloe area of the county, was detained on suspicion of withholding information about the killing.
It is understood he had been living in Glasgow for the last six months.
The younger man, from Annagry, Co Donegal, was detained on suspicion of possession of firearms on the day of Mr Donaldson's killing.
The former senior Sinn Fein officer, from west Belfast, was shot dead at a remote cottage in Co Donegal on April 4 2006.
No-one has been charged over the 56-year-old's murder and the arrest is understood to be the first by gardai.
A senior officer described the case as "complex".
Just months before his death, Mr Donaldson publicly revealed that he had been working as an informer inside the republican movement for years.