Belgium this week marks the first anniversary of deadly Islamic State-claimed attacks on the Brussels metro and at the airport which left 32 people dead.
Following is a summary of what is known of the young men who carried out the March 22, 2016, attacks and the investigation.
3 suicide bombers
Najim Laachraoui and Ibrahim El Bakraoui blew themselves up in the crowded departure hall of the airport early on March 22 last year.
Shortly afterwards, Ibrahim’s brother Khalid attacked Maalbeek metro station in the European Union quarter.
Laachraoui, 24, a one-time electrical engineering student who had fought in Syria, is believed to have been the bomb-maker for the November 2015 Paris attacks which left 130 people dead.
Ibrahim El Bakraoui, 29, was well known to Belgian police and had tried to go to Syria in 2015 only to be stopped on the Turkish border.
His brother Khalid, 27, is also suspected of having help Laachraoui find safe houses for other jihadists, many from Brussels like themselves, who carried out the Paris killings.
2 failed bombers
Mohamed Abrini, widely known as the “Man in the Hat” from video footage of the airport attack, failed to detonate his suicide bomb and was filmed fleeing on foot back to central Brussels where he disappeared.
Osama Krayem, 24, seen with Khalid El Bakraoui at a metro station carrying huge backpacks before going their separate ways, also failed to go through with his suicide attack.
Krayem, born in Sweden to Syrian parents, apparently hid himself among fleeing refugees to return to Europe from Syria in 2015.
Both Abrini and Krayem were arrested in Brussels in early April.
Abrini, 32, was a childhood friend of Salah Abdeslam, the only survivor of the Paris jihadist team and who grew up in the gritty Molenbeek district of Brussels.
Abrini and Abdeslam were filmed at a service station en route to Paris just before the 2015 attacks there.
In the immediate aftermath of the Brussels attacks, the authorities carried out extensive raids in the Belgian capital and beyond and these continue, although at a much reduced pace.
Those detained as a result are mostly suspected of having helped prepare the metro and airport attacks.
Smail Farisi, 32, and Bilal El Makhoukhi, 28, still detained, are believed to be the most important figures.
Farisi is said to have set up a safe house for the metro attack while Makhoukhi, known by his nom de guerre from Syria of “Abu Imran”, has been linked to Ibrahim El Bakraoui.
Who actually gave the order for the Brussels attacks remains unknown.
Federal Prosecutor Frederic Van Leeuw says be believes the order came “from very high up” in the Islamic State (IS) hierarchy.
Investigators have reportedly identified Osama Atar, a Belgian-Moroccan veteran extremist in his 30s who served time in US prisons in Iraq, as the main suspect.
A laptop computer found near the safehouse used for the airport attack apparently shows that the Brussels jihadists had been in close contact with Atar.
Attack switched to Belgium?
The laptop computer also appears to show that the team initially intended to carry out another attack in France but panicked as the police closed in.
The key moment was Abdeslam’s arrest on March 18, just days before the attacks in central Brussels not far from the family home.
“Taken by surprise by the speed of the investigation (the jihadists) decided to hit Brussels,” the federal prosecutor’s office said.
The laptop also contained what some refer to as Ibrahim El Bakraoui’s last testament in which he expressed fear at being tracked down before they could act.