Workers on Friday plan to wrap bee-proof netting around blooming trees in the parking lot of an Oregon shopping center in an attempt to prevent the deaths of more bees.

Portland-area bee experts with the Xerces Society for Invertebrate Conservation estimate at least 25,000 bumble bees have died in the lot since last weekend. The bees were clustered under dozens of linden trees.

Oregon Agriculture Department officials confirm thousands of dead bees.

The Oregonian reports that Agriculture officials are working with the Xerces Society, the city of Wilsonville and the distributor of an insecticide.

State officials say tests to confirm the cause of the deaths could take two or three more days. They are checking for insecticides as well as possible natural causes.

Wilsonville is southwest of Portland.