A man in his 30s is being questioned in connection with the 2005 murder of a woman in Co Louth.
Irene White, 43, was found murdered in her home beside Ice House Hill Park on 6 April 2005.
The man, who was arrested in Monaghan this morning, has been brought to Dundalk Garda Station for questioning.
Ms White, a mother of three, was stabbed a number of times.
In a previous statement, gardaí said they believed the perpetrator killed Ms White in the kitchen of her house before fleeing across the back wall.
They are describing today's arrest as significant.
The man was not previously known to gardaí and is a new suspect in the case.
Two years ago the Serious Crime Review Team - known as the cold case unit - re-examined all the files related to the original investigation.
Last November, Ms White's daughter Jennifer also made a fresh appeal for information on the killing.