Police have launched a murder investigation and a man has been arrested after the death of a two-year-old boy.
The alarm was raised at around 5.45pm on Sunday when officers were called to a house in Cheriton Drive, Bolton, Greater Manchester, after reports that the toddler had gone into cardiac arrest.
Ambulance crews also attended and the boy was rushed to the Royal Bolton Hospital, where he was later pronounced dead.
A Home Office post-mortem examination will take place at Manchester Children's Hospital to ascertain the cause of his death, a spokesman for Greater Manchester Police said.
A 22-year-old man has been arrested on suspicion of murder and remains in police custody for questioning.
Detective Superintendent Jon Chadwick said: "The investigation is in the early stages and a dedicated team of detectives will be working to establish exactly what happened."
The toddler has been named locally as Rio Smedley.
His mother Kirsty Smedley is said to be in her 20s and is pregnant by the man now under arrest, who is not the dead boy's father. She also has a four-year-old daughter, Ella, from another previous relationship.
The family moved into the two-bedroom housing association property from another part of Bolton around two months ago.
Neighbour Natalie York, 31, a mother of eight, said she saw the drama unfold. "I saw the police and ambulance around half four and heard the boy's mum screaming and the ambulance guy running out of the house with the boy in his arms. I feel sick. I've got a two-year-old. I just hope it is an accident, it's horrible."