Authorities in Oregon and Washington are still investigating the origin of mysterious tar balls that have recently appeared along the Pacific Northwest coastline.

These sticky substances have been observed from Long Beach, Washington, to Yaquina Head, Oregon. The initial reports surfaced on May 19, when various state agencies detected several tar balls near the mouth of the Columbia River. On Sunday, the Oregon Department of Fish and Wildlife revealed that the substance is “petroleum-based,” hinting at a possible oil spill. However, the precise source remains unidentified. The agency anticipates releasing more detailed findings in a few days as crews continue to search for additional tar balls.

By May 21, at least 10 birds had been found covered in oil between Long Beach and Lincoln City, Oregon, with three of them succumbing to their condition. The affected birds were all common murres. According to ODFW, more wildlife has since been discovered impacted by the tar, though the exact number remains unclear. A multi-agency task force, including the Oregon Department of Environmental Quality, Washington Department of Ecology, and the U.S. Coast Guard, has been scouring the coastline for affected areas.

The public is advised against touching the tar or handling wildlife that has come into contact with it. Anyone who does come into contact with tar should wash it off using soap or dish detergent and water. Additionally, it is important to avoid contact with gasoline or diesel fuel.