Published Wednesday, 04 December 2013
David Black died in an ambush on the M1 in November last year. (© PA)
Mr Black, a 52-year-old father of two, was shot dead on the M1 motorway near Lurgan in Co Armagh as he drove to work at Maghaberry Prison in November last year.
The man was detained along with a 34-year-old man on Monday during searches in counties Cavan and Leitrim, linked to dissident republican activity.
They were arrested under Section 30 of the Offences against the State Act, 1939.
The 51-year-old was released on Tuesday night, but the second male man remains in custody at Cavan Garda Station.
© UTV News