A 65-year-old detainee died at a U.S. military prison in southern Iraq on Saturday after suffering a heart attack, military officials said late Saturday night.

The unnamed prisoner “complained of chest pains and was immediately transported to the Camp Bucca field hospital by the medics,” according to a U.S. military release.

“The detainee went into cardiac arrest while in the intensive care unit and died after all lifesaving efforts failed to resuscitate him.”

The man was pronounced dead of natural causes around 2 p.m., officials said. Military officials have ordered an autopsy performed before the release of the remains to his family; that is standard practice with all detainee deaths while in U.S. custody, according to a military spokesman.

Camp Bucca is one of three existing and expanded prison facilities that are expected to replace the Abu Ghraib prison near Baghdad.

U.S. military officials have said they will transfer all detainees out of Abu Ghraib by early next year, then hand the complex back over to Iraqi control.

Abu Ghraib was the site of the notorious prison abuse scandal that erupted in April 2004.

The other two facilities that will house detainees are Camp Cropper and Fort Suse. Renovations to Fort Suse, in northern Iraq near Sulaymaniyah, were completed in late October and hundreds of detainees will be transferred there in the coming months.