Detectives investigating the murder of PC Ronan Kerr in the North have arrested a second man today.
The 40-year-old suspect was stopped in a car on the road between Omagh and Ballygawley in Co Tyrone at 8.20am.
He is being questioned about the murder the 25-year-old Catholic PSNI officer in Omagh on Saturday, and also about a significant cache of weapons and explosives discovered by police in nearby Coalisland on Tuesday night.
A 26-year-old suspect arrested in Scotland yesterday in relation to the arms find has now been re-arrested over the murder.
Both suspects are being questioned at Antrim police station.
As the 40-year-old man was arrested, police also seized a vehicle for examination.
PSNI assistant chief constable Drew Harris said yesterday: "Detectives from serious crime branch who are investigating Ronan's murder have made a significant discovery of arms and munitions - one of the most significant in recent years."
The weapons haul - found in stolen vehicles in garages on the Mountjoy Road in the Co Tyrone town - included Kalashnikov rifles, ammunition, timer power units, detonators, incendiary bombs, components for rocket launchers and other explosive devices, and a quantity of explosives, possibly Semtex.
The first man arrested was taken into custody in Renton, Dunbartonshire.
He was initially questioned about the Coalisland find but was re-arrested in police custody today in connection with the murder.