Up to five people have been found dead, including a woman and children, at a house in Western Australia in Perth's north-eastern suburbs.
Police could not confirm exactly how many people have died, but confirmed multiple bodies were found at the house in Coode Street, Bedford.
Officers arrived at the scene around midday local time, after a man went to a regional Western Australian police station today and provided information about the incident.
That man, believed to be in his 20s, is now in custody.
Police have not yet said what the relationship was between the man in custody and the deceased.
There was no information about the ages of those who have died, beyond the fact some children were involved.
Police have blocked off traffic around the scene of the incident and have a heavy presence there, with forensic officers among those on site.
Homicide detectives will now take the lead in the investigation.
Assistant Police Commissioner Paul Steel said the investigation was still at a "very early stage" but described the incident as a tragic event.
"It is tragic not only for the family and the friends, it is also tragic for those first responders who are forced to attend such scenes," he said.
Assistant Commissioner Steel said officers were still working to determine the timeline of what happened.
"We are three hours into this investigation, I have no further detail in relation to those who are present at the location," he said.
This is the second major incident in Western Australia this year.
In May, a 61-year-old man killed his wife, daughter and four grandchildren, before killing himself.