A woman died and a man was seriously injured in a two-vehicle crash south of Toodyay last night.
The RAC Rescue helicopter was sent to the scene on Toodyay Road to help the injured man. He was flown to Royal Perth Hospital for treatment and was in a critical condition last night.
Two children were taken to Swan District Hospital by ambulance. A St John Ambulance spokeswoman said their injuries were not serious.
Insp. Mark Bordin said last night the road was expected to be closed for about 10 hours while major crash officers investigated.
Insp. Bordin said police redirected heavy Perth-bound traffic at the Toodyay- Northam Road intersection.
The crash happened when a Honda Civic sedan collided with a Mitsubishi Triton about 6.30pm.
A woman in the Honda Civic died and a man in the same car was seriously injured.
A woman and two children in the Triton suffered minor injuries.
Sgt Dayna Rigoir, from Northam police, urged motorists to be careful on country roads, avoid fatigue and be cautious overtaking after a horror weekend in the district.
Police had redirected Perth-bound traffic at the Toodyay-Northam Road intersection.
Toodyay was packed yesterday with racegoers attending a picnic race meeting at the historic racecourse.
The meet, which includes the $15,000 Toodyay Cup, had been expected to draw a crowd of more than 3500.