A 25-year-old man has been arrested on suspicion of murder after the death of an eight-month-old baby boy.
The boy, from Rochdale, died after being taken to hospital suffering from multiple injuries, Greater Manchester Police said.
A 24-year-old woman has also been arrested on suspicion of causing or allowing the death of a child and the pair remain in custody.
Police were called by the ambulance service shortly before 9.30am on Tuesday September 6 over concerns for the welfare of a child in the Spotland area of Rochdale.
An eight-month-old baby boy was taken to hospital but died on Thursday.
The 25-year-old man is being questioned in custody after being arrested on suspicion of murder and of causing or allowing the death of a child.
Det Chief Insp Jamie Daniels said: "This is a deeply distressing investigation involving a small child.
"Our thoughts at this time are with the family, friends and all others within the local community who may be affected by this incident.
"If anyone has any information that may assist the investigation please call 101."