A 6-year-old girl has died in hospital this morning following an incident in Mill Park last night.
Emergency services were called to an address in Kellaway Crescent about 7.50pm after reports of a stabbing.
On arrival police located a man, woman and a girl with critical injuries.
The 39-year-old woman died at the scene and the 40-year-old man was taken to hospital under police guard in a critical condition.
The girl was also taken to hospital in critical condition where she later died.
At this stage detectives believe all parties are known to each other and the matter is being investigated by the Homicide Squad.
Anyone who witnessed the incident or with footage or further information is urged to contact Crime Stoppers on 1800 333 000 or submit a confidential report online at www.crimestoppersvic.com.au