Acting on emergency calls Monday night, they hurried to a rural road in northern Switzerland where horrified motorists reported a long trail of blood - what they believed was evidence of a brutal crime.
A police statement Tuesday said officers followed the blood for 12 miles (20 kilometers) to the town of Kuettigen only to find that a butcher's supply van had spilled its cargo.
A barrel of pork blood had overturned inside. The van had been headed for a local sausage factory.