Detectives arrested the man at 11 o'clock last night for questioning about the murder of 36 year Olivia Dunlea O'Brien at her home in Pembroke Crescent in Passage West.

Gardai initially believed she died following a fire at her home - however a post mortem revealed she died as a result of stab wounds.

Last nights arrest came after Gardai upgraded their inquiry from one of suspicious death to murder following receipt of post-mortem results.

The state pathologist Dr Marie Cassidy found Olivia Dunlea O'Brien died from stab wounds.

Initially it had been thought the 36 year old died as result of a fire at her two storey semi-detached house which she shared with her three children in Passage.

However gardai became suspicious after technical experts found two seats of the fire during a forensic examination of the scene.

One seat of the fire was downstairs and the other was upstairs where firefighters recovered the body of the woman from the main bedroom which was badly damaged.

Ms Dunlea O Brien was separated and her three children, two boys and a girl, were staying with their father when she was fatally assaulted and the house set alight.

Gardai are expected to begin questioning a 35 year old man in connection with her death this morning.

He was arrested at his home in Passage West under Section 4 of the Criminal Justice Act last night and can be held for up to 24 hours before being released or charged.