Officials said satellite images of the area are inconclusive regarding claims by the Satellite Sentinel Project that it had detected what appeared to be three mass graves and a pile of bodies in the city of Kaduglia, The Washington Post reported.
That doesn't mean the graves don't exist, said Princeton Lyman, the U.S. envoy to Sudan.
"We can't confirm the conclusion in the Sentinel project that there are mass graves in Kadugli," said Lyman, citing U.S. intelligence reports.
U.S. officials said regardless of whether there are mass graves, the Sudanese government and its allies appear to be committing human rights abuses in South Kordofan. Officials said civilians, perhaps hundreds, have been killed and more than 70,000 forced to flee their homes in recent fighting.
"We're deeply concerned," Lyman said.
Earlier this month South Sudan split from the north, making it the newest country in the world. The Sudanese government of Omar al-Bashir has denied targeting civilians. He is accused of committing genocide in a separate conflict in the western region of Darfur.
Officials said it is difficult to prove many claims because the Sudanese government has banned Western news organizations.