Gardai investigating the murder of 10-day-old baby Johnny McCarthy arrested two suspects yesterday.
This brings the total number of people arrested to eight -- six of them on suspicion of withholding information about the incident.
Inquiries into the toddler's death have now been officially upgraded to a murder investigation.
The infant suffered a severe head injury and bruising to his body in Lusk, Co Dublin, before he died in hospital earlier this month.
Garda technical bureau officers spent four days examining the scene, while a post-mortem examination was carried out by State Pathologist Marie Cassidy.
The baby had travelled with his parents from their home in Navan to Lusk. At about midnight the baby was taken to hospital and died two hours later.
Gardai yesterday arrested two suspects in Balbriggan, Co Dublin, and they were being questioned last night at Balbriggan and Whitehall garda stations. The officer in charge of the Dublin North division, Chief Superintendent Gerry Phillips, said last night that they were making good progress with their inquiries into the death and a dedicated team of gardai had been assigned to the case.
But he issued an appeal to members of the public who had information about what had taken place that night and were reluctant up to now to come forward.
Chief Supt Phillips urged potential witnesses to think again about their decision and contact the gardai in the strictest confidence with any information they may have.
The garda confidential phone line is 1800 666111.