The family of seven was travelling from South Australia towards Melbourne when the crash occurred about 8.30am.

Two adults both in the 20s were taken to hospital as was a female infant and a male toddler who were all taken by road ambulance for observation.

Update: 10.30am: AT least six people, including five children, one believed to be just 16 weeks old, have been assessed at the scene of a rollover this morning on the Western Freeway at Mount Rowan.

The occupants of the vehicle, a male driver and the children have all been taken to Ballarat Base Hospital for observation, but there are no obvious injuries in what looks like a miracle escape.

The car was travelling towards Melbourne when it has lost controlled and rolled into the median strip about 300m east of the Midland Highway turn off.

The car ended up on its side, but did not roll over.

Police at the scene said it was fortunate that a person on leave from the Army was first on the scene and was able to assist in getting the passengers out of the car.

A truck driver travelling to Laverton was also one of the first on the scene. He said he had also assisted in the earlier crash near Armstrong near Ararat where a man was killed and two people were airlifted to hospital with serious injuries.

Update, 9.46am: There were actually five children in the green Ford Territory. The male-driver, a p-plater, had been driving overnight from South Australia.

It is understood a person from the Army was first on the scene and helped rescue the trapped adult and children.

Police say it was a "miracle escape".

The adult and five children have been taken to Ballarat Base Hospital for observation.

Update, 9.20am: The children are walking around while the adult is on a stretcher. One lane of traffic is still open but motorists are being urged to avoid the area if possible.

There are about 12 rescue crews on the scene.

The car has rolled onto the median strip.

A truck driver first on the scene had only just witnessed the Ararat fatal crash earlier this morning.

Earlier: An adult and three children, including a four-month-old infant, have been involved in a car crash on the first day of the Easter long weekend.

The vehicle rollover happened on the Western Freeway, Melbourne-bound, about 300 metres past the Midland Highway at Mount Rowan just before 9am.

All are conscious and breathing and out of the vehicle.

More to come.