Motorists were stuck in a traffic jam for more than two hours in Ahero, Kisumu County, on Friday evening.
Police blamed a hearse for the snarl-up, but said heavy rain and overlapping vehicles on the Kisumu-Nairobi road made it worse.
Vehicles going to and leaving Kisumu were stuck in the jam.
Police frantically worked to ensure traffic flow.
Nyanza Regional Traffic boss Andrew Naibei said the traffic jam was caused by mourners transporting the body of Mr David Ongudi, who was an official in Siaya County.
He was being ferried to his rural home in Ahero for burial on Saturday.
But mourners, who were in a convoy of vehicles, drove around the town causing a traffic jam.
"Other road users were trying to evade the jam and decided to create their own diversions that ended up creating the traffic jam," said Mr Naibei.
The situation was made worse by the heavy rains that pounded the area and made the road slippery.
Mr Naibei called for calm as police worked to ensure traffic flow.
"Drivers and passengers should be patient because we are sorting it out. In the next few minutes, traffic should be normal," he said.