Video feedbackVideo settingsA baby thrown 15 metres from a car in a horrific highway rollover came perilously close to being hit by oncoming traffic, police said this morning.

Leading Senior Constable Darren Skelton told radio 3AW the girl was thrown onto the east bound lanes of the Western Freeway at Melton after the vehicle she was in lost control and flipped up to four times.

The infant was one of eight people - including three more children - injured when the Tarago crashed off the highway. She and her mother today remain in a critical condition.

Police are investigating the possibility a strong gust of wind may have blown the vehicle off the road.

Leading Senior Constable Skelton said the baby was "very lucky not to be hit by another car". "(Another motorist) actually stopped and thought it was a doll until it started moving its arms," he said.

Police said the five-month-old girl, who is believed to have been thrown from a baby capsule, was lying on the road for up to 40 seconds before a relative who was also injured in the crash rescued her.

Mr Skelton said he arrived at the crash site within within minutes and found a "big mess".

"Being a 'people mover' there was a lot of stuff in the car which had been strewn out of the car," Leading Senior Constable Skelton said.

"Two of the children were still in the back of the car strapped in. The baby of course was out of the car in the mother-in-law's arms."

The infant's 30-year-old mother was cut from the crushed vehicle. She was taken to The Alfred hospital. Three other adults were taken to the Western Hospital. All are believed to be from the same family.

All the children were taken to the Royal Children's Hospital, three with minor injuries.