The Morobe Provincial health advisor in Papua New Guinea says other prisoners could be affected with a heart virus which claimed the lives of four inmates earlier this year.
Dr Likei Theo says he will assess the state of the inmates at Lae's Buimo prison later this week.
In his autopsy report, the national pathologist, Dr Phillip Golpak, declared the four died from a viral infection of the heart.
Dr Theo says the crowded living conditions could have contributed to the contraction and spreading of the disease.
He says the remainder of the prisoners will need to be checked to ensure they don't have the virus.
"We need to establish what percentage of the prisoners are actually either carriers or been infected by the virus.... we need to determine that.... we need to do further tests on the rest of the prisoners about three or four hundred of them"
However Dr Theo says efforts to test all the prisoners would rest on the availability of equipment.
30 prisoners at the same jail had suffered a mysterious muscle wasting condition earlier this year, but began to recover after their diet was improved.
