Three children dead, one critical after car plunges into lake

Three children are dead and another sibling has been critically injured after a car driven by their mother plunged into a lake in Melbourne's west.

Emergency services were called to the accident off Manor Lakes Boulevard, near Pedder Street, in Wyndham Vale in Melbourne's west about 3.40pm.

The young victims - all aged under six - were pulled from the water by rescuers.

One of the children killed is thought to be just 18 months old, while a second child is believed to be seven years old.

Another believed to be between five and six years old is fighting for life at the Royal Children's Hospital.

The mother of some or all of the children is under police guard in hospital with minor injuries.

It’s believed police are investigating whether the woman intentionally drove the car into the lake.

An adult driver, who is believed to be the children's mother, suffered minor injuries and was taken to the Royal Melbourne Hospital in a stable condition.

7News understands she is under police guard.

One witness said a man had tried to rescue the trapped children and pulled out a boy for paramedics to try and save him.

"Travis jumped into the water and smashed the back screen of the car and got one little boy out," the witness told Fairfax Radio.

"It's a horrible scene."

She said the car was travelling along Manor Lakes Boulevard but went straight over the road into the lake.

Police said the exact circumstances of the accident are yet to be determined.

They confirmed a female driver and four children, all aged under six, were in the car when it went into the lake.