Police are continuing to question two men and a woman arrested after the death of a seven-week-old baby boy from severe head injuries.
The badly injured infant was taken to the Royal Oldham Hospital in the early hours of January 25 and was later transferred to the Royal Manchester Children's Hospital, where he died.
Greater Manchester Police said that the man and the woman were expected to remain in custody overnight and that they were not in a position to name the baby, who lived in the Clarksfield area of Oldham.
The 23-year-old woman, thought to be the child's mother, and a 35-year-old man originally arrested on suspicion of assault were rearrested on suspicion of murder and conspiring to pervert the course of justice, police said.
A 26-year-old man is also under arrest on suspicion of murder and conspiring to pervert the course of justice.
Detective Inspector Andy Cunliffe, from GMP's major incident team, said: "This is a tragic case in which a very young baby has lost his life and we are determined to find out exactly what the circumstances were that led to him suffering such injuries.
"News of the death of such a little boy will no doubt come as a great shock to people and I would like to try and reassure the community as much as I can that we have a team of detectives dedicated to working on this investigation, and they will today be interviewing the three people in our custody.
"If anyone has any information at all that they believe may assist us with our inquiries, then please get in touch and tell us what you know."