The police said the two suspects were involved in hiding the van used in the attack.
The prison bus was shot at in Kalutara last month killing seven people including an underworld member.
Underworld member Aruna Udayashantha, alias Samayan, was killed in the shooting incident. Two prison officers were also killed in the shooting incident.
A woman who gave refuge to the Kalutara prison bus attackers was arrested earlier this month.
Another person was also arrested in connection to the incident. (Colombo Gazette)