Investigators have made progress in piecing together who carried out last week's terrorist attacks in Brussels and why, but key questions remain open.
WHAT WE KNOW:
- The attacks were carried out on the morning of March 22 by at least four people. Two suicide bombers blew themselves up at the Belgian capital's international airport, and a third dropped off an explosive device and then left. A fourth attacker blew himself up in an underground train at the Maelbeek station, near the seat in Brussels of the European Union's main institutions.
- The three dead suicide bombers have been identified. Two were Brussels-born brothers who had criminal records in Belgium, but not for terrorist offences: Ibrahim El Bakraoui, 29, and Khalid El Bakraoui, 27. Ibrahim was one of the suicide bombers at the airport, while Khalid was at the Maelbeek station. Najim Laachraoui, a 24-year-old Belgian national who had long been sought in connection with last year's Paris terrorist attacks, was identified Friday as the second suicide bomber who died in the airport attack.
- The attacks left 32 dead, in addition to the three attackers. Four of the victims died in hospital, the Health Ministry said Tuesday. All casualties have been identified: 17 of the victims were Belgian and 15 had foreign nationalities. They included the citizens of 13 different countries, according to the Belgian Foreign Ministry.
- The attacks left around 340 people wounded. As of Thursday afternoon, 80 remained in hospital, of whom 41 were in intensive care, the Health Ministry said. Citizens from 20 foreign countries have been counted among the injured, according to the Belgian crisis centre.
- The Islamic State extremist group has claimed responsibility for the attack, accusing Belgium of "attacking Islam and its people." Belgium is part of a US-led coalition that has carried out airstrikes against Islamic State in Syria and Iraq.
- The investigative findings communicated by Belgian prosecutors increasingly point to a link between the Brussels suicide bombings and November's terrorist attacks in Paris. Laachraoui and Khalid El Bakraoui are suspected of having rented real estate in Belgium allegedly used by the Paris attackers. Traces of Laachraoui's DNA were found on explosive vests used in Paris.
WHAT WE DON'T KNOW:
- The identity of the third airport attacker, who is still thought to be at large, remains unknown. Police have released a surveillance video and images of the suspect who has been dubbed "the man with the hat," asking the public to help identify him. A man detained in the days after the attacks was identified by Belgian media as the suspect, but he was released due to a lack of evidence.
- Media reports of a second attacker at the Maelbeek metro station have not been confirmed by Belgian officials. The state broadcaster RTBF said it was unclear whether the unidentified man, who was captured in surveillance video carrying a large bag, was still alive.
- It remains to be determined if other people helped the Brussels attackers, for instance with logistical assistance. German police last week arrested two men in connection with the Brussels attacks, but a prosecution spokeswoman later said there was no evidence to implicate either of them.