The inmates, both males, a 38 and a 40 year old were found with leaves suspected to be marijuana during a routine search when they returned to prison.
Authorities are investigating to determine how they acquired the leaves.
The bust has raised further questions about how many other inmates could be in possession of illegal substances inside the prison compound.
The two prisoners are serving their sentences at Tafaigata Prison and will appear in court at a later date for the latest alleged offence.
This was one of the reported cases of drugs found by the police in the past week.
Another involved a man who was apprehended at a nightclub with leaves suspected to be marijuana.
The third report involves the arrest of two people following a raid at a hotel in Apia.
Police seized drugs in the raid. No other details have been released about the raid.
However, Loop Samoa has been reliably informed that one of the suspects is a prominent civil servant.