U.S. officials are investigating an unusual outbreak of tuberculosis (TB) infections in people who had spinal surgery. They suspect the culprit is a potentially tainted bone repair product, according to news reports.

More than 100 people may have been exposed to TB bacteria through this product, called FiberCel, during spinal surgeries that occurred this spring, according to The Washington Post. FiberCel is a putty-like substance made from human bone tissue that’s used during various orthopedic and spinal surgeries, the Post reported.