Given the large number of recent terror attacks worldwide, there is a growing concern over the security issue in the maritime world. Aim of this paper is to address a scenario pertinent to the maritime security problem using the evacuation simulation software tool EVI. The vessel chosen for this case study is a 13-deck cruise ship. The scenario investigated deals with the evacuation of a large density populated area within the vessel, where an explosive device has been placed and assesses the potential loss of life, according to the distance of the agents relative to the explosion blast. Three different positions of the explosive device are examined in this study and for each position six different cases are examined, in which the effect of prior warning to the explosion is taken into consideration. In the first case, the explosion takes place at the beginning of the simulation (t=0) in order to replicate such a scenario in which those agents within the restaurant are un-alerted to the presence of the explosive device. In the rest of the cases the explosion takes place after warning times of 0.5, 1, 1.5, 2 and 2.5 minutes respectively in order to assess the sensitivity of the fatality rate and evacuation to prior warning time.