Police are asking for two motorcyclists who may have witnessed a fatal crash in Waroona to come forward.
A 28-year-old man was driving a 1999 Holden Commodore wagon north on the South Western Highway around 9.40pm on December 21 when it left the road and crashed into a tree near Tallathalla Road.
The man, from Waroona, died at the scene.
Three other passengers were injured and taken to hospital.
Major Crash investigators would like to speak with two motorcycle riders who were travelling together, in a southerly direction along the South Western Highway between Pinjarra and Waroona around 9.30pm and who may have seen the crash.
Investigators are asking the riders to come forward.
Anyone who saw the crash or the Holden Commodore prior to the crash, or can identify the two motorcycle riders, is asked to call Crime Stoppers on 1800 333 000 or report online at www.crimestopperswa.com.au.