Two motorbikes were seen racing at high speed before one rider was killed when he crashed and was flung off a Melbourne bridge last night.
The 32-year-old died about 10pm on Sunday after travelling south over the Bolte Bridge at Port Melbourne and taking an exit ramp where he crashed into a barrier.
"Investigators wish to speak to the rider of a second motorbike, which was observed riding alongside the vehicle immediately prior to the crash," police said in a statement.
"Witnesses have reported the two bikes may have been racing at high speed."
Investigators are appealing for dashcam footage of the crash or the preceding reported race.
Later on Monday, a woman driving a Winnebago was killed when the vehicle veered off the Great Alpine Road and crashed into a tree at Eurobin.