CAMBRIDGE, Mass. — During the July 1993 Srebrenica massacre in the former Yugoslavia, UN peacekeepers failed to adequately prevent the mass killing of over 7,000 men and boys, according to a review by the UN Secretary General. The infamous crime was the worst on European soil since World War II, Kofi Annan said in 2005.

"May we all learn, and act on, the lessons of Srebrenica," the former UN head said.

Sadly, it appears that history may have repeated itself.

As many as 7,000 internally displaced men, women, and children were reported missing in the town of Kadugli, South Kordofan, Sudan on June 20, 2011. Their last confirmed location was just outside the “protective perimeter” of the United Nations Mission in Sudan compound, where they had sought shelter and safety near UN peacekeepers.

More than two years later, the whereabouts of these internally displaced persons (IDPs) remain unknown. Unlike what followed Srebrenica, however, it appears that no high-level investigation into their fate has yet to be undertaken by the UN Department of Peacekeeping Operations or any other UN agency.

The civilians, many from the Nuba ethnic group, had fled their homes when fighting between the Sudanese government and rebels from the Sudan People’s Liberation Army-North broke out in early June 2011. This ongoing conflict has displaced thousands of civilians in South Kordofan, Blue Nile and elsewhere.

During the time they disappeared, we were part of the Harvard Humanitarian Initiative (HHI) team monitoring their position from over 400 miles above as part of the Satellite Sentinel Project (SSP). SSP, founded in 2010 by actor George Clooney and the Enough Project, uses satellite imagery analysis and ground reports to document threats to vulnerable populations in Sudan and South Sudan.

Before and after the 7,000 IDPs went missing, we and our colleagues analyzed imagery captured by DigitalGlobe high-resolution satellites that contained evidence consistent with house-to-house searches and freshly dug mass graves in Kadugli.

On the day they disappeared, the displaced civilians were reportedly ordered by Sudanese forces to vacate their camp adjacent to the UN mission’s facility or face reprisals. The IDPs were told to report by that afternoon to a soccer stadium in Kadugli town. There, they were led to believe they would hear a speech about humanitarian assistance from the governor of South Kordofan. It is not known if they ever made it to the stadium.

It should be noted that South Kordofan’s governor, Ahmed Haroun, is currently under indictment by the International Criminal Court. He faces 42 charges for allegedly committing crimes against humanity and war crimes in the Darfur region of Sudan.

The Central Reserve Police (CRP), a Sudanese paramilitary unit that reported to Haroun when he allegedly committed crimes in Darfur, was present in Kadugli during this time and purportedly under his command. According to our team’s analysis, the CRP had established a compound within a few dozen meters of the UN compound weeks before the IDPs began gathering there.

In "Sudan: Anatomy of a Conflict," a report released in May by HHI’s Signal Program on Human Security and Technology, we examine archival satellite imagery and public accounts related to these events, including the build-up of CRP forces near the compound.

According to the Independent, for example, some of the IDPs who found shelter at the camp were shot near the protective perimeter by Sudanese forces in the days prior to June 20. Eyewitnesses said that their bodies were dragged away from the camp like “slaughtered sheep.”

The Egyptian contingent of UN peacekeepers stationed there reportedly stood by as these and other alleged attacks occurred. Additional reports from that time also suggest that UN personnel kept the gate of the compound closed to IDPs seeking sanctuary. These accounts and other available data, while chilling, do not reveal any new insights about where the 7,000 IDPs went.

However, this review does present a compelling case for the UN to finally launch a formal inquiry into what exactly transpired at the UN mission’s protective perimeter in June 2011. Any UN investigation needs to conclusively answer these three critical questions about the Kadugli incident:

First, what role did Haroun and his forces, including the Central Reserve Police, play in the disappearance of the IDPs? Second, what did the UN Mission in Sudan do or not do to protect these people before they vanished? Finally and most importantly, where are the IDPs now, and are they alive or dead?

UN Secretary-General Ban Ki-moon should follow the example of his predecessors and order an independent investigation to discover what actually happened in Kadugli. As in Srebrenica, UN officials and peacekeepers who ailed to adequately execute their mandate during the Kadugli incident should be held to account.

The people of Kadugli and the Nuba Mountains deserve to know the fate of the missing 7,000 who were neighbors, friends, and family members. Conversely, the international community, to prevent similar situations from transpiring yet again, needs to know why and how this incident was allowed to happen.

Nathaniel A. Raymond is the director of the Signal Program on Human Security and Technology at the Harvard Humanitarian Initiative. Issac L. Baker is the imagery analysis manager at the Signal Program on Human Security and Technology at the Harvard Humanitarian Initiative.