Police investigating the deaths of a woman in her 20s and her two young daughters say they are not looking for anyone else in connection with the case.
The three people found at a house in Little Lever, Bolton, have been named locally as Tiffany Stevens and her daughters, Caisie, aged 3, and 1-year-old Darcie.
Police have not confirmed their names.
Superintendent Rick Jackson, of Greater Manchester Police said:
"This is an incredibly tragic incident and we have specialist officers supporting the family at this unimaginably difficult time.
What is thought to have been a gas engineer was seen this morning at the mid-terrace house the family lived in on Arthur Street.
Neighbour Annmarie Crossland, 36, said she was first alerted something was wrong when Ms Stevens' brother and ex-boyfriend were heard "screaming and shouting" in the alleyway at the back of the house before another neighbour rang 999 around 3.30pm yesterday.
Ms Crossland said:
"Paramedics arrived first and shot off down the back, then another came and then just all police covered the whole street..."
She described Ms Stevens as a "brilliant mum" and said her own four children played with Ms Stevens daughters.
Ms Crossland added: "They were gorgeous little kids. Great, really nice. She would take them to the park and into Bolton. They were very friendly."