CAIRO, July 28 (RIA Novosti) - Surgeons at Mansoura University's Children's Hospital in Egypt have successfully separated a set of 8-month-old conjoined twins, Egyptian MENA news agency reported on Tuesday.

The twins, Saber and Bilal Abdel Rahman, were joined by the hip. They partially shared the same backbone and spinal cord and had one digestive tract and urethral system between them.

The 12-hour operation ended late Monday evening and the patients are in the intensive care unit, but said to be in good condition. The boys were taken to the children's hospital immediately after their birth.

Two contradicting theories exist to explain the origins of conjoined twins. The older and more generally accepted theory is fission, in which the fertilized egg splits partially. The second theory is fusion, in which a fertilized egg completely separates, but stem cells find like-stem cells on the other twin and fuse the twins together.