The family of Denis Donaldson have raised concerns that their mobile phones may have been monitored after new revelations about the surveillance of a journalist investigating his killing.
The concerns follow a BBC Spotlight investigation which revealed new details about the monitoring of the phone data of former BBC security correspondent Brian Rowan without his knowledge.
Mr Donaldson, who had been an informer within Sinn Féin, was shot dead near Glenties in 2006.
His family told the BBC that they are concerned they too may have been subjected to some form of phone data surveillance.
