A 10-month-old baby boy is among three children who were found dead at a house in Bristol on Sunday, police have said.
The other victims were a seven-year-old boy and a three-year-old girl, it is believed.
Officers were called to the property in the Sea Mills area of the city on Sunday morning by a member of the public concerned for the welfare of the people inside.
The victims, who have not been named by detectives, were found inside the property and pronounced dead at the scene just after 12.40pm.
A 42-year-old woman was arrested on suspicion of murder and taken to hospital to be treated for non-life threatening injuries. She remains in custody.
Post-mortem examinations are not expected to be completed until the middle or the end of this week “at the earliest”.
Detectives have not said whether the children were related to each other or the arrested woman.
Avon and Somerset Police has referred itself to the Independent Office for Police Conduct watchdog over prior contact.
Chief Inspector Vicks Hayward-Melen told reporters at the scene on Monday: “Uniformed officers from the neighbourhood policing team will be in the area in the coming days to provide reassurance and support to the local community, so please speak to us if you have any concerns or worries.
“It’s important to stress we are treating this as an isolated incident and we don’t believe there to be any ongoing risk to the wider community.
“We’ve been humbled by the community response to this tragedy.
“At a time of great sadness and disbelief, we’ve seen spontaneous acts of care and support.
“Within hours of the incident occurring, a local church was opened up for people to gather and mourn.
“This is what being in a community is all about and we’d like to thank all those who continue to offer this important and selfless service.
“The death of such young children is a great shock to the whole community and this incident has had a profound and deep impact on all of us in the police.
“We’ll be making sure all those involved in the response and the subsequent investigation are given any welfare support they may need.
“I know people will be eager to have answers, but the major crime investigation team are in the very early stages of what will be a highly sensitive, complex and thorough investigation, and it will take time to establish all the facts.
“We anticipate we’ll need to carry out further inquiries at the scene for the rest of the week and there will be some cordons in place while we do this.”
People who believe they have information which could help the investigation have been asked to call 101 quoting reference 5224042788 or visit the force’s website.