A man was being questioned in Edenderry Garda Station last night, following the suspected murder of a teenager in the Co Offaly town earlier yesterday.
Gardai confirmed that a murder investigation had begun when a post-mortem established that the 19-year-old man died from stab injuries.
The victim was named as Mr Christopher Groome, with an address at Church View Heights, Edenderry.
Gardai had been called to the scene of the incident - a mobile home encampment - shortly after 3 a.m. The injured man was taken to Tullamore General Hospital but died two hours later.
A middle-aged man was arrested at about 8 p.m. and was being held overnight under Section 4 of the Criminal Justice Act.
The Assistant State Pathologist, Dr Marie Cassidy, was also due to carry out a post-mortem at Galway's University College Hospital last night on the body of a 37-year-old woman.
The woman was taken ill while sitting in a car outside her flat in the Riverside Estate area of the city on Sunday night. She was taken to University College Hospital where she died a short time later.