MIAMI — A worldwide search is on to find blood donors with a rare genetic variation to help save a 2-year-old South Florida girl battling cancer.

Zainab Mughal has neuroblastoma and needs life-saving transfusions. But finding compatible donors is immensely challenging, because she's missing a common antigen most people carry in their blood, called "Indian B."

Florida-based OneBlood says the donors must have "A'' or "O'' type blood and be Pakistani, Indian or Iranian; and that even within these ethnic groups, fewer than 4 percent of people have the genetic variation.

Three donors have been found thus far, including a person in England, but Zainab will need more blood than they can provide.

OneBlood is offering to coordinate compatibility testing anywhere in the world.