UPDATE 9.30PM THURSDAY: A Royal Melbourne Hospital spokeswoman said the woman's condition was no longer considered "critical" but was serious.
UPDATE, 9.45am THURSDAY: Ambulance Victoria spokesman John Mullen said the driver of a car which hit three horses at Gisborne South this morning was in a critical condition.
"A woman in her late 60s was driving. She suffered head and facial injuries and was taken to The Royal Melbourne Hospital in a critical condition," Mr Mullen said.
"A passenger was uninjured but was treated for shock and also taken to the Royal Melbourne for further observation," he said.
"A MICA unit attended from Melbourne and also the Riddells Creek ambulance."
POLICE are looking for the owner of three horses which died this morning after a car hit them on Millett Road, Gisborne South.
Gisborne's Leading Senior Constable Mustafa Emin said a single car was travelling west as three escaped horses were running in the opposite direction on Millett Road.
"It was still dark, it happened about 6.30am," Leading Senior Constable Emin said.
"The driver received serious injuries and was transported to The Royal Melbourne Hospital.
"We are still making inquiries as to where the horses came from."
Ambulance Victoria, the Country Fire Authority and State Emergency Service also attended the scene.
A passenger was uninjured and Millett Road was closed for about an hour.
Leading Senior Constable Emin said two horses died on impact and a veterinarian had to put-down the third horse at the scene.
"It is a good reminder for people to make sure their animals are secured," he said.
If you are missing three horses, contact Gisborne Police Station on 5428 2500.