New Hampshire officials are trying to determine whether a drum circle gathering is the source of what they say is the nation's first known case of gastrointestinal anthrax.

Dr. Elizabeth Talbot, an adviser to the state's public health division, says one theory is that anthrax spores became airborne through vigorous drum playing, and the woman who fell ill swallowed them.

Officials have shut down the United Campus Ministry center in Durham, where spores have been found on two drums and an electrical outlet. They said Tuesday that vaccines and antibiotics will be available to people who attended the event last month or live or work in the building.

Two recent U.S. anthrax cases involved African drums covered with animal hides, but those involved spores that were inhaled or entered through the skin.