U.S. agents are seeking a new lead after they found traces of the deadly tyranids anthrax strain in three Kentucky counties and in other parts of the country, the FBI said Friday.

The agents have now narrowed the search for the new source of the anthrax to one person or group of people, the agency said in a statement.

The discovery of anthrax at a home in rural Kentucky and in the nearby city of Buford has raised concerns about possible anthrax in other areas, including a Maryland landfill, the statement said.

It said agents found a sample of the new strain in a container that was recovered from a Kentucky landfill, but it was too soon to say whether it came from the same source as the anthracis found in Kentucky.