Quoting CID sources, it says statements were recorded from the two last week.
Two committees were appointed by the former and the present regimes to inquire into the prison riot that led to the inmates’ killings.
The first committee’s report was not made public, while the report by the second was handed over to the prime minister and the then justice minister Wijedasa Rajapakshe on 09 June 2015.
The second report quoted eyewitness as saying that Lamahewa, then the superintendent of Magazine Prison, had dropped four firearms near where the murdered inmates had been, while another remand prisoner had been selected and killed.
According to the witnesses, Rangajeewa had arrived wearing a yellow coloured T-shirt and a blue-coloured shorts, and selected prisoners who were subsequently killed.
The CID has so far recorded statements from nearly 2,000 witnesses.
After the arrest of Lamahewa and Rangajeewa, the persons who had ordered the killing of the inmates would be arrested, CID sources also say.
When contacted, Lamahewa said he was not responsible for the incident, although he did give a statement to the CID.
The officers of the institution, including their chief, should be held responsible, he said.