A woman has died in a crash in the state’s South West.

Police say the 28-year-old was driving her Toyota Hilux along South Western Highway in Boyanup last night when she failed to negotiate a bend.

The car left the road and smashed into a tree.

The woman died at the scene.

Meanwhile, four people have spent the night in hospital after a serious crash in Williams yesterday morning.

Volunteer firefighters worked for more than an hour to free people from the car, after it crashed into a tree.

Two adults were flown to Royal Perth Hospital where they remain in a serious but stable condition

Two children were initially taken to Narrogin Hospital, but their injuries were deemed too serious and were flown to Perth Children’s Hospital.

One is in a stable condition and the other is critical.

Anyone with information about either crash is urged to contact Crime Stoppers on 1800 333 000.