A man in his 40s has been arrested in connection with the murder of IRA informer Denis Donaldson.
The leading Sinn Féin member, was shot in the rural Glentis area of Donegal in April 2006.
It happened months after he was exposed as an agent who had worked for MI5 for over 20 years.
The suspect is being detained at Letterkenny Garda station.
It comes just a week after a 74 year old man was charged with witholding information over the killing.
Patrick Gillespie, with an address at Craigvar Street in Glasgow, was granted bail by the Special Criminal Court last Friday.
Anyone with information has been asked to contact Gardaí in Letterkenny at 074 9167100, the Garda confidential line at 1800 666111 or any Garda station.
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