Leila de Lima, head of the Commission on Human Rights, said that witnesses to the other killings, including five police officers, had come forward after the arrest of members of the Ampatuan family, who have been charged with killing 57 civilians last month and of rebellion against the central government.

She said that militiamen loyal to Andal Ampatuan Snr, a clan leader whose family dominates local politics in the province of Maguindanao, had carried out many other murders and secretly disposed of the bodies. “We are looking at a minimum of 200,” she said. “These are victims of the same clan and the private armies. Given the right opportunity there will be witnesses who can exactly pinpoint these mass graves.”

The decision casts a cloud of uncertainty over pending adoptions in the country and will halt a surge in placements of Vietnamese children with U.S. citizens in recent years.

The announcement followed a report from the U.S. Embassy in Hanoi that was first obtained by The Associated Press that alleged pervasive corruption and baby-selling in Vietnam’s adoption system.