The prisoners were shot following a prison riot over poor living conditions and restricted family visits in June 28, 1996, the officials said.
Dr. Salem Fergani, a committee member of the NTC, said there is much to be done to reach the truth of the killings, CNN reported Sunday.
"To be honest, we were not prepared to deal with such human massacres, so we request the assistance of the international community. We need specialists in the field to help us in identifying the victims ... this is a national mission. The families of these victims have the right to learn the truth about their deceased sons," he said.
Former guards at the prison Abu Salim prison led officials to the mass grave and provided details of the massacre Aug. 20, CNN said.