The family of a two-year-old boy who police suspect may have been murdered have paid tribute to a "loving son" who will be "greatly missed".
Rio Smedley was rushed by ambulance from his house in Bolton, Greater Manchester, as his pregnant mother Kirsty screamed in anguish, neighbours said.
Rio, who has a sister, Ella, aged four, was taken to the Royal Bolton Hospital after reports he had suffered a cardiac arrest but doctors were unable to save him and he was pronounced dead on Sunday evening.
On Monday, police said they had launched a murder inquiry with a man aged 22 under arrest, the Press Association reported.
In a statement released through Greater Manchester Police, the boy's family said: "Rio was the loving son of Kirsty, brother of Ella, grandson of Karen and Paddy, Gordon and Yvonne, nephew of Shaun and Jason.
"He will be greatly missed and the family now ask for some peace during this hard time."
A steady stream of visitors, some inconsolable with grief, left flowers and soft toys outside the two-bed housing association property on Cheriton Drive in Bolton.
One bouquet of flowers said simply, "RIP Little Man" in tribute outside the house.
Neighbours said Miss Smedley and her partner, a man in his 20s believed to be from Wigan, had only moved into the property around two months ago. No carpet could be seen on the stairs or wallpaper on the walls.
Locals said Ms Smedley is pregnant by her partner, who is not the dead boy's father.
Her daughter is also understood to have a different father according to neighbours.
Natalie York, 31, a mother-of-eight, who lives nearby said she saw the drama unfold yesterday after police were called.
"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, from Greater Manchester Police, 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."
Mick Callaghan, 47, a relative of Miss Smedley, said she had met her current partner around 12 months ago and suggested the pair had a stormy relationship.
A Home Office post-mortem examination will take place at Manchester Children's Hospital to find out the cause of death, a police spokesman added.
Bolton council would not say whether the family was known to social services.
A spokesman for the local authority said: "We were saddened to hear about the death of Rio and our thoughts are with his family at this difficult time.
"Professional support will be made available to the family.
"As this matter is subject to a police investigation we are unable to comment on the events surrounding the case."
Anyone with information is asked to call police on 0161 856 5740 or the independent charity Crimestoppers, anonymously, on 0800 555 111.