West Virginia officials investigating reports of a powder in the air and on some vehicles in the mid-Atlantic have determined the source: pollen.

Final results from the dust samples collected Friday in the state’s Eastern Panhandle indicated the material is predominantly pollen, with trace amounts of mineral matter, the West Virginia Department of Environmental Protection said in a statement Monday. The samples were analyzed by West Virginia University’s Department of Geology and Geography.

The agency began investigating after residents reported seeing the substance across multiple counties late Thursday night.

Social media users posted about seeing the powder in the air and on cars on Friday in West Virginia, northern Virginia and Maryland.

The West Virginia lab was testing the dust to determine if it was related to dust storms in the Midwest, the Department of Environmental Protection statement said.

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The Associated Press contributed to this article.