Two young children whose bodies were found, along with their mother, in a house in Gwynedd had been suffocated, say police.
Izaak Stevens, two, his brother Phillip Stevens, five, were both found in their bedroom at home in Trawsfyndd, Gwynedd, on Sunday night.
The body of their mother Melanie was found hanging in the same bedroom.
North Wales Police confirmed they are not looking for anyone else in connection with the deaths.
Det Chief Insp John Hanson said they were still trying to establish the "catalyst" that caused the event.
Officers attended the house at around 2000 GMT on Sunday after concerned relatives reported that Ms Stevens and her two sons had not been seen for some time, Det Chief Insp Hanson confirmed.
When officers arrived at the property, they had to make a forced entry.
Det Chief Insp Hanson said: "This is a very, very sad and difficult investigation.
"We continue to gather evidence and the coroner is appraised.
"Family liaison officers continue to work closely with the family and contact has been established with victim support."
Neighbours and people in the village said the family moved to Trawsfynydd about 18 months ago from the Midlands.
Ms Stevens, a mother-of-five and orginally from Blaenau Ffestiniog, has three older children, believed to be living with their father.
An inquest into the deaths will be held in due course.