The two have not surrendered despite President Rodrigo Duterte's directive to the freed criminals because of the good conduct time allowance law that surrendered to the authorities.
Justice Undersecretary Mark Perete said they are still waiting for the suspects Joszman Aznar and James Anthony Uy.
The two have until September 19 to surrender.
Two other suspects have already surrendered before the Chiong sisters rape-slay case, Ariel Balansag and Alberto Caño
Senator Richard Gordon will invite former Justice secretary Vitaliano Aguirre II to the next Senate justice committee hearing on the Good Conduct Time Allowance Law.
It was to ask Aguirre about his implementation of the department order that required Department of Justice approval before the Bureau of Corrections released heinous crime convicts.
Department Order No. 953 was issued in November 2015 by former Justice secretary Benjamin Caguioa.
Gordon said he would likely invite incarcerated Senator Leila de Lima to the hearing, but he does not see any reason to do so now.
De Lima followed Caguioa as secretary of the justice department, and was one of the creators of the implementing rules and regulations (IRR) for Republic Act No. 10592, extending the scope of the GCTA.
