An official with the United Nations says evidence is growing against Syrian President Bashir al-Assad.

Navi Pillay, head of the U.N.’s human rights office, said a panel investigating the abuses in the Syrian civil war has found “massive evidence” showing the crimes were initiated at the highest levels of the Syrian government including the head of state.

Pillay later denied knowing the names on the investigator’s secret list of suspects but her remarks about a head of state being involved goes against all previous U.N. investigations into war crimes. Investigators, who work independently of Pillay’s office, have previously said evidence points to high levels of the government but did not implicate al-Assad.

The U.N. Human Rights Office says that accountability for war crimes should be part of any agreement ending the civil war.

The question about al-Assad remaining in power is a point of contention between the United States and Russia as the superpowers work to bring the sides of the war to the peace table.