An initial probe into a suspicious house fire which killed three people is likely to last several days.
Emergency services were called to the scene in Heaton, Bolton, shortly after 2am today as neighbours reported they heard an explosion before smoke filled the property.
Firefighters rescued a woman from the upstairs of the semi-detached address in Albert Road West and she was taken to hospital but died a short time later.
A further search led to the discovery of two bodies in the back kitchen, where it is thought the blaze started before it spread throughout the house.
The middle-aged couple living at the house were named locally as Hassan and Mona Rafie. It is thought they were Iranian and that an elderly relative may have been staying with them.
Divisional Commander of Bolton, Chief Superintendent Dave Hull, said: "Three people have tragically lost their lives and our thoughts are with their loved ones at this time.
"We have launched a joint investigation with the fire service and experts from both agencies will be working together to find out what happened and why.
"I know people, especially in the local community, will be shocked and anxious to find out what has gone on and as soon as we are able to provide further updates we will do so.
"I do not want to second guess or prejudice the outcome of these investigations but in the interests of absolute transparency want to make it clear that we are treating these deaths as suspicious and are not looking for anyone in connection with the fire at this time."
Speaking at the scene, he added: "From our initial assessment of the scene we can't easily establish a non-suspicious cause.
"We are not presently looking for anyone in connection with the inquiry but the investigation could change tack if we get new information.
"The people in the house are not known to the police in any significant or relevant way."
He said they had no intelligence to suggest that threats had been made to the occupants.
The woman who died has been identified but the two bodies remain in the house as forensic examinations continue.
Assistant County Fire Officer Peter O'Reilly said he thought the investigation at the scene would last for several days.
A couple who lived next door, who did not wish to be named, said they were woken by an explosion, which apparently came from the kitchen area of the property. They then saw smoke fill the building.
Another close neighbour, Maria Taylor, 48, said she was woken by the sound of fire engines and then heard smashing glass as firefighters broke in to gain access to the property.
She said: "There were some flames initially and then a lot of smoke coming from the kitchen area. It was going up the stairwell, up to the landing.
"An ambulance then arrived and a body was brought out. They were doing CPR on the person in the garden at the front. The fire was put out pretty quickly."
She said she thought the couple had two children who were away at university.
"They were a lovely, lovely family," she said: "They have lived here for about 10 years. I don't know them well but we would always say hello to each other and exchange pleasantries.
"I think they were Iranian. They have been trying to sell their house for quite a while - I think they wanted to downsize after the children left home."
Mrs Taylor said she had not noticed any disturbances at the property while the couple had lived there.
She said: "There has never been any trouble before. Last night was quiet, like any other night. It all feels a bit surreal, like a film."
She said Mr Rafie used to run a computer business in nearby Chorley Old Road, while his wife worked at Next.
Stuart Whittle, who lives opposite, said he arrived home in the early hours to a fog of smoke.
He said: "As I got closer I could see fire engines and police cars. I didn't think anyone was in the house." H e believed an elderly relative had been staying with the couple.