MIAMI (Reuters) - An Afghan prisoner collapsed and died at the Guantanamo detention center while using an exercise machine, legal and military sources said on Thursday. Awal Malim Gul, who was accused of being a Taliban commander and an al Qaeda associate, died at the Guantanamo Bay U.S. Naval Base on Tuesday. Gul, 48, had been using an elliptical trainer, a stationary exercise machine used to simulate stair-climbing or running. Arrangements were being made to repatriate his body, the legal source said. He had been held without charge at Guantanamo since October 2002. Gul is the seventh captive to die at Guantanamo since the detention center opened in January 2002. One other died of natural causes colon cancer and five died of apparent suicide. Nearly 800 men have been held at the camp, which still holds 172 detainees.