Dozens of people diagnosed with an extremely rare eye cancer in Huntersville, North Carolina, and Auburn, Alabama, has stumped scientists who are trying to figure out how so many people developed ocular melanoma.

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So far 18 people in Huntersville and as many as 36 who attended Auburn University have been diagnosed with the disease, according to CBS News. The cancer is generally diagnosed in just 6 of every 1 million people.

Four friends who all went to Auburn were diagnosed with the rare eye cancer, and when one of them mentioned it to her doctor at Philadelphia's Sidney Kimmel Cancer Center, her doctor was shocked.

"Most people don't know anyone with this disease," oncology Dr. Marlana Orloff told CBS News. "We said, 'OK, these girls were in this location, they were all definitively diagnosed with this very rare cancer – what's going on?'"

Orloff and others are studying these cancer patients to try to find out what caused so many people in one area like Auburn, Alabama to develop such a rare form of cancer.

Despite the diagnoses, officials with the Alabama Department of Health have said there is no evidence for a cancer cluster in Auburn, but officials at Auburn University told CBS they hope awareness and research will help figure out and prevent ocular melanoma.

Scientists studying the cancer patients in Huntersville, including their environment, were not able to find anything linking the cases in the town, which is north of Charlotte, according to WSOC-TV.