The FBI says it is investigating a suspicious letter containing white powder that was sent to the headquarters of the Samaritan's Purse charity in western North Carolina.

The agency said the letter was received Friday at the charity's headquarters in the town of Boone. State and local agencies are participating in the investigation.

The charity is run by the Rev. Franklin Graham, the son of evangelist Billy Graham. The charity has made headlines in recent months for its work in fighting Ebola in West Africa.

FBI spokeswoman Shelley Lynch said she didn't have information on how many people may have handled the letter at the charity. The FBI noted that while most letters with white powder are hoaxes, it is taking all necessary precautions during the investigation.