Scurvy killed off nearly half the colonists at one of the North America's first French settlements, according to a new study of their bones.

French colonists established the settlement at Saint Croix island between present-day Calais, Maine and St. Stephen, N.B., in 1604.

Nearly half the 79 settlers died during a harsh winter at the early European outpost. The island is now an international historic site.

To probe what killed the colonists, researchers analysed the disinterred bones from seven burial sites before they were reburied on the island in 2003.

Dr. John Benson, director of medical imaging at Mount Desert Island Hospital in Bar Harbor, Maine, and his team used a technique called multi-detector computed tomography to study the bones.

The technology allows scientists to take faster, higher-quality images than conventional CT scanners, without destroying artifacts.

"We were able to visualize the entire skull from every angle, inside and out," Benson said in a release.

"Scans of the skull and leg bones revealed a thick hard palate in the mouth and an extra layer of bony tissue on the femur and tibia, which we believe resulted from the internal bleeding associated with scurvy."

Cut marks on one of the skulls suggest the surviving colonists tried to perform an autopsy to understand what was killing their fellow settlers.

Scurvy is a disease caused by a lack of vitamin C. It is marked by weakness, anemia, gum disease and internal bleeding. Eating citrus fruits and some vegetables can prevent scurvy.

Benson presented the results on Monday in Chicago at the annual meeting of the Radiological Society of North America.