Military coroners have ruled as homicides the deaths in December of two prisoners at a U.S. base in Afghanistan, a military spokesman said.

A U.S. Army investigation of the deaths continues, said Col. Roger King, a spokesman for U.S. forces at the base in Bagram, Afghanistan.

The two prisoners died last Dec. 3 and Dec. 10 at the makeshift prison in the U.S. compound at the Afghan base north of Kabul. The autopsies that labeled the deaths as homicides found that the men had been beaten, and one had a blood clot in his lung, King said.

American forces are holding an unknown number of prisoners at Bagram. A Pakistani official has said the prisoners include Khalid Sheikh Mohammed, the top Al Qaeda leader captured over the weekend in Pakistan.

A human rights group called in December for an independent investigation of allegations of torture at Bagram.