Koroit police are seeking dash-cam footage of a motorcyclist reaching shocking speeds in "horrendous" conditions on Wednesday.
Sergeant Pat Day urged anyone with a vehicle camera who was driving on the Princes Highway around 11.54am to check their footage.
"A person was spotted riding at 133 kilometres per hour in the rain today," he said.
"The motorcycle was heading towards Warrnambool. The Koroit van passed it just after the entrance to Tower Hill. The road was slippery and we didn't try to intercept as conditions were horrendous. The motorcyclist was last seen going past the Tower Hill cemetery."
Sergeant Day said "quite a few" cars pulled over during the incident.
"We are wondering if any of those cars had dash-cam footage," he said.
"It was a blue motorbike with full fairings. The rider appeared to be wearing black leathers."
Anyone who has information is urged to contact Koroit police.
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