Gardaí are still questioning a man in connection with family feuding in Limerick that is thought to be connected to the killing of Mr Kieran Keane near the city this week.
Mr Keane was killed just hours before two brothers from a rival family - Eddie and Kieran Ryan - returned having been missing for almost a week.
Officers are questioning a man in his 30s, who was arrested in the Tipperary area yesterday morning. A woman arrested at the same time has been released without charge, while another man and woman arrested on Thursday evening were also released without charge last night.
Gardai said they expect more arrests to be made over the weekend.
Father-of-two Kieran Keane was found shot in the head on a roadside with his hands tied behind his back.
Officers have been interviewing Mr Keane's nephew Mr Owen Treacy, who suffered serious stab wounds in the same incident on Wednesday night.
Despite Garda fears of reprisals and an escalation of violence, Limerick city was again quie7t last night with no major incidents reported.