Stawell Sergeant Bill Alford said the woman in her mid-50s was killed at about 7.30am on Wednesday after her car hit a tree.

"A vehicle driving along the Navarre Road left the road and hit a tree," he said. 

Sgt Alford said there was no suggestion alcohol or drugs were a factor.

He said investigators were still trying to determine the speed the car was travelling at when it left the road.

"We are still investigating the circumstances surrounding this terrible event," he said.