• Sri Lanka’s president declared on Monday a conditional state of emergency that gave the security services sweeping powers to arrest and interrogate people, and to conduct searches. A dusk-to-dawn curfew remains in effect in Colombo, the capital, and major social media and messaging services remained blocked by the government.

• Within hours of the bombings, Sri Lankan security services arrested at least 24 suspects, and by Tuesday the number had grown to 40, suggesting the government knew where key members of Thowheeth Jama’ath could be found. The group was under surveillance, and the authorities had learned as far back as January that radical Islamists possibly tied to the group had stockpiled weapons and detonators.

• A forensic analysis of body parts found that most of the attacks had been carried out by lone bombers, but that two men had attacked the Shangri-La Hotel in Colombo.

• The leader of National Thowheeth Jama’ath, Mohammed Zaharan, is a known extremist who has spent time in both India and Sri Lanka, and who in recent years has preached hateful messages online.

• One of the suicide bombers was arrested a few months ago on suspicion of having vandalized a statue of Buddha, a highly provocative act in Sri Lanka, a Buddhist-majority island nation in the Indian Ocean.

• Before the Islamic State made its claim, intelligence and counterterrorism analysts in Washington were scrutinizing possible ties between the militant group and the attackers, but as of Monday afternoon they had not reached any definitive conclusions.

What we know about who was killed and where

• The attacks took place at three churches and three hotels on Sunday morning in three separate cities across the island. Two more explosions happened in the afternoon in and around Colombo, one at a small guesthouse and the other at what was the suspects’ apparent safe house. Three officers searching for the attackers were killed in that blast.