Sri Lankan police say two bomb experts were among the suicide attackers who struck churches and hotels on Easter and all those directly involved in the bombings are either dead or under arrest.

Acting police chief C.D. Wickramaratne also said in a statement late Monday that explosives the group stacked for use in more attacks have been seized.

The bombings killed 257 people and wounded hundreds at three churches and three hotels. Seven suicide bombers died at their targets while another exploded his device later at a guesthouse after his device failed at a leading tourist hotel. A ninth killed herself to avoid capture by police at her home.

Authorities arrested dozens of people after the bombings and repeatedly said another attack from the Islamic State-linked extremist group was possible.