Police in Northern Ireland are continuing to question a 26-year-old man arrested in Scotland in connection with the murder of Constable Ronan Kerr.
Mr Kerr, 25, was killed when a car bomb exploded in Omagh on Saturday.
The man was held in West Dunbartonshire on Wednesday and has been taken to Northern Ireland for questioning.
Police have said the arrest is linked to a weapons find in the Coalisland area of east Tyrone on Tuesday evening.
The man was arrested in Renton and is said to have been working in the area.
He is being questioned at Antrim PSNI station.
Assistant Chief Constable George Hamilton of Strathclyde Police said the arrest was made at the request of the PSNI.
"Needless to say we were acting in support of them at their request, and given the tragic circumstances leading up to this, we were happy to do this, and to make the arrest on their behalf under the terrorism act," he said.
Speaking at a news conference at police headquarters in Belfast, Assistant Chief Constable Drew Harris, said the weapons were found on Tuesday night inside stolen cars in a garage at Mountjoy Road in Coalisland.
The weapons included four rifles, detonators, component parts for rocket launchers, incendiary bombs and explosives, possibly Semtex.
"Everyone in Northern Ireland is very much safer today because these munitions have been taken out of circulation," he said.
ACC Harris said the find was "the most significant in recent years".
The arms found were:
•Four Kalashnikov rifles
•Six loaded ammunition magazines
•Timer power units
•Components for rocket launchers and other explosive devices
•Quantity of explosives, possibly Semtex
Police said the items were being "fast-tracked for forensic examination" and formed one line of inquiry in the Ronan Kerr murder investigation.
"The seizure was made in a garage unit on the Mountjoy Road. Inside the unit, police officers uncovered a number of stolen vehicles and inside those vehicles, a significant amount of arms and munitions," ACC Harris said.
"This investigation into Ronan's murder will continue in the coming days and weeks with the same determination and professionalism which resulted in last night's discovery."
Anne Murphy lives near to where the explosives were found, and said there had been a major police operation.
"It really took off about six o'clock on Tuesday evening," she said.
"I've never seen anything like it before, in the amount of resources that have been in the area.
"There have been jeeps, there have been mini-buses, large vans, with possibly forensic vehicles included.
"They've been here continuously, manning the place. The area's been blocked off."