A murder inquiry may be launched by detectives investigating what caused the Shaw gas blast.
Jamie Heaton, 2, was killed in the explosion, which destroyed his home and two others.
The youngster, described by his heartbroken family as a "happy loving little boy" who was "full of laughter", was killed as he watched TV in the front room of the family's terraced house in Shaw, near Oldham.
His mother Michelle survived the carnage after she momentarily stepped into the yard to hang out washing to dry.
Her husband Kenny and two other children, Jodie and Jack, were not at home and spared serious injury.
In tribute, the victim's family said: "Jamie was a happy loving little boy - precious son to Michelle and Kenny and loving little brother to Jodie and Jack.
"Jamie's life was full of laughter. He loved going to preschool, playing with sand and water and going to the park. He touched the hearts of all who knew him and will be missed by all."
The killer blast, around 11.15am on Tuesday, left neighbour Andrew Partington, 27, in a serious condition in hospital with burns.
But after initial police and fire service investigations Mr Partington faces "significant questions" a senior officer said today.
Police are at his bedside at Wythenshawe Hospital in Manchester waiting to be given the go-ahead by doctors to question him.
Sources confirmed a domestic argument involving the injured man took place in the hours before the blast.
Steve Heywood, Assistant Chief Constable of Greater Manchester Police (GMP), told a press conference in Shaw: "We have had some information to suggest it may not be accidental so we are treating it as a suspicious death and therefore a homicide investigation is undertaken."
According to locals, the property occupied by Mr Partington was rented from landlord and local businessman Iltaf Hussain.
The massive explosion flattened number 11 Buckley Street, where Jamie lived, and number 9, where Mr Partington lived.
The two houses are separated by an alleyway.
It is understood Mr Partington, who worked as a joiner had only moved into the property around six weeks ago.
Mr Heywood added: "One of the early indications was that it may not have been an accident, therefore we will always then up the ante and treat it as a suspicious death inquiry.
"There might have been some precursor event, like a domestic incident. All those things are still in our thinking at this time."
Mr Partington is still under sedation and officers will await medical advice on when he is fit to be quizzed by police.
"He was a resident on the street at the time," Mr Heywood added, "and he is obviously somebody who we have significant questions for.
"His partner is currently being spoken to by specially trained officers in relation to what information she can give in relation to this investigation."
Mr Heywood said it was only by chance that Jamie's mother was not in the house when it was reduced to rubble in the explosion.
"The victim Jamie was in the house, we believe in the front room, watching TV and his mother had just slipped out into the back yard, hanging out washing," he said.
"What that mother must be going through must be unbelievable, so our hearts go out to her."
Prime Minister David Cameron paid tribute to emergency services at the scene and told MPs at question time in the Commons he wished "all speed" to police to "get to the bottom of anything that might have happened here or anything that might have gone on".
In Shaw, flowers were left in tribute at the edge of the police cordon still in place around the devastated streets at the centre of the blast.
One card read: "Sleep tight little one, heartfelt sympathy to all the family. God bless from all at Holyrood Nursery."
A cuddly toy had a handwritten note attached, reading: "Jamie, I'm giving you my Bob the Builder so you can play with him in heaven. Good night, God Bless xx."
Surrounding properties were also severely damaged and structural engineers will have to check each house before residents can return.
National Grid said the incident was not caused by a leak from its gas distribution pipes in the street.
Five homes on Buckley Street were extensively damaged during the incident and the firm's workmen have not been able to carry out checks on internal pipes, meters and gas appliances in the houses, with the area now being treated as a crime scene.
Councillor Jean Stretton, from Oldham Council, said: "The response from the local community and partner groups to this tragic event has been heart-warming.
"In the face of such adversity everyone has pulled together in a fantastic community effort."
The council has launched a Distress Fund to help the residents of around 100 houses evacuated from their homes.