SALEM -- Tests found no pesticides, pests or disease in the more than 1,000 honeybees found dead last month along a road in the Portland suburb of Sherwood.
Oregon Department of Agriculture spokesman Bruce Pokarney said Thursday the results lend more weight to the theory that the bees were killed by passing cars as a swarm from nearby hives crossed a busy highway.
Pokarney says Oregon State University tested for 230 active ingredients, and they all came back as non-detectable.
Samples from the hives were also tested for pests and disease, with similar results.
Last year, pesticides were blamed for tens of thousands of bees found dead in a shopping center in Wilsonville.
Two companies that sprayed the insecticide were fined.