A man remains under police guard in hospital with critical injuries as homicide detectives investigate a woman's death in Melbourne's southwest.
Emergency services were called to a property in Hoppers Crossing about 1.15pm on Thursday, following reports of a disturbance.
Police apprehended a 51-year-old Hoppers Crossing man at the scene who was behaving erratically.
The 40-year-old woman - from Darley in Bacchus Marsh, 50 kilometres west of Melbourne - was found unresponsive inside the property.
She died at the scene.
The man was taken to Royal Melbourne Hospital with serious upper body injuries, and remained there under police guard in a critical condition as of Friday morning.
The pair are believed to know each other.
Homicide squad detectives are investigating but are not looking for anyone else over the incident.
