The investigating judges at Cambodia's Khmer Rouge tribunal have confirmed the resignation of several staff members, who say they quit to protest the judges' decision to close their investigation in a controversial third case.

In a terse statement released Sunday, the German and Cambodian co-judges say they “welcome the departure” of all staff who fail to recognize their “sole responsibility” in the case. They also say they expect to complete their work in a competent and timely manner despite the departures.

The Cambodia Daily newspaper says four permanent staffers and one consultant, all with Western names, have quit the investigating judges' office at the U.N.-backed tribunal since April. It quotes consultant Stephen Heder saying in a May 5 resignation e-mail that the judges closed their probe of Case 003 “effectively without investigating it.”

The resignations are the latest blow to the credibility of the court, which is charged with investigating and prosecuting crimes committed by the Khmer Rouge during its murderous rule in the late 1970s.

International prosecutor Andrew Cayley publicly objected after the two judges closed their investigation in Case 003, which is believed to involve two senior military officers. In a request to have the probe re-opened, he revealed that the investigators had neither questioned the suspects nor visited suspected mass graves.

The judges responded by accusing Cayley of revealing confidential information. An appeal of their order that he retract the statement is pending.

The tribunal, made up of both Cambodian and international jurists, has already convicted a notorious Khmer Rouge jailer and is to open the trial of the top four surviving Khmer Rouge leaders later this month.

Prime Minister Hun Sen has objected to any further prosecutions, saying Cambodian society could be torn apart if the tribunal proceeds with a planned third and fourth cases.