Two men are still being questioned this evening in connection with the murder of a PSNI officer in April of last year.
Constable Ronan Kerr was killed when a bomb exploded under his car in Omagh, Co. Tyrone.
Investigating officers arrested a 39 year old from Omagh this morning - he's being questioned about incidents related to last year's killing, but not for murder.
He was detained during searches carried out by the PSNI in the town.
Elsewhere, a 22 year old man, arrested in Milton Keynes in England yesterday, is still being held for questioning.