Police have arrested a man in connection with the murder of a two-year-old boy in Bolton, Greater Manchester.
The alarm was raised at around 5.45pm yesterday when officers were called to a house in Cheriton Drive, Bolton, after reports that the toddler had gone into cardiac arrest.
Ambulance crews also attended and the boy, named locally as Rio Smedley, 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.
His mother, Kirsty Smedley, is 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 yesterday.
"They're just a normal family," Ms York said.
"I saw the police and ambulance around half four yesterday and heard the boy's mum screaming and the ambulance guy running out of the house with the boy in his arms.
"The ambulance shot off with flashing lights and sirens.
"I feel sick. I've got a two-year-old. I just hope it is an accident, it's horrible."
Detective Superintendent Jon Chadwick said: "I would like to extend my sympathies to this young boy's family and friends at what is clearly a very difficult and emotional time for everyone.
"The investigation is in the early stages and a dedicated team of detectives will be working to establish exactly what happened."