The U.S. Justice Department has begun a war crimes investigation into the notorious killing of a suspected Iraqi insurgent at Abu Ghraib prison in 2003.

Reports Tuesday said federal prosecutor John Durham had begun calling witnesses before a grand jury in Virginia, near the U.S. capital. The grand jury will be considering whether there is enough evidence to charge suspects with war crimes and torture.

The prisoner, Manadel al-Jamadi, died while in CIA custody. In the much-reported case, al-Jamadi got the nickname “the iceman” because his handlers tried to preserve his body to hide his death by packing ice around him.

Official investigations ruled the death a homicide, and the CIA referred the case to the Justice Department for possible prosecution.

A U.S. military jury in 2005 found a Navy commando officer, Lieutenant Andrew Ledford, innocent of charges he beat al-Jamadi to death.

Suspicion over the years has also focused on a CIA interrogator named Mark Swanner, who questioned the victim shortly before his death.

The Justice Department has refused to comment on the case, saying the investigation is ongoing. Under U.S. law, grand jury proceedings are conducted in secret.