Brussels- Brussels disclosed the identity of the three suicide bombers in the airport and the subway; they are the Bakraoui brothers and Najem Alchraoui.

Raids, arrests and forensic analysis are some of the tools investigators are using to get to the bottom of who was behind the attacks in Brussels, which killed 31 people and wounded 270 others.

Two of the bombers were brothers. And one of the bombers at the airport appears to be a man authorities named as a suspect in the Paris terror attacks.

Belgian federal prosecutor Frederic Van Leeuw identified Ibrahim El Bakraoui as one of two suicide bombers at the Brussels airport and his brother, Khalid El Bakraoui, as the man behind a deadly suicide blast about an hour later on a train near the Maelbeek metro station.

Surveillance images showing three men pushing luggage carts through the airport have played an important role as authorities work to pinpoint the suspects.

The second suspect was filmed by surveillance cameras in the Brussels metro on Tuesday carrying a large bag alongside Khalid El Bakraoui, whom prosecutors have identified as a suicide bomber.

Turkish President Recep Tayyip Erdogan said that in July 2015, Belgian authorities had the chance to detain Ibrahim el Bakraoui, now identified as one of the suspected suicide bombers who struck Brussels on Tuesday.

Erdogan said that Turkey warned Belgian authorities of Bakraoui’s terrorist ties when it deported him into the custody of the Netherlands, but that the Belgian native was released anyway.

Belgian authorities, the Turkish president said, responded soon after saying he had a criminal record but no known ties to terrorism.

“These two deceased suicide bombers had lengthy criminal records,” he said, “but were not linked to terrorism,” Van Leeuw said.

Ibrahim El Bakraoui had been sentenced in October 2010 by a Brussels criminal court to nine years behind bars for opening fire on police officers with a Kalashnikov during a robbery.

Van Leeuw said that a raid came after a tip from a taxi driver led them to the northeast Brussels area of Schaerbeek.

The driver recognized the men shown in surveillance footage and told authorities he’d driven the men to the airport before the attacks. Police raided the area where the driver told them he’d picked up the men.

Investigators found chemical products and an ISIS flag during a house search in Schaerbeek, the federal prosecutor’s office said in a statement.

On Wednesday, they made another significant find: Ibrahim El Bakraoui’s will.

Police found the airport bomber’s will on a computer in a trash can in Schaerbeek, Van Leeuw said. The will indicated Bakraoui “needs to rush” and “no longer feels safe.”

In the Schaerbeek residence, authorities found 15 kilograms of the explosive TATP and screws among the bomb-making materials there, Van Leeuw said.

French prosecutors have said that the bombs used in the November Paris attacks — which, like those in Brussels, ISIS claimed responsibility for — were also made from TATP, which stands for Triacetone Triperoxide.

The more authorities dig, the more connections they find between the coordinated attacks in Brussels and the string of shootings and bombings four months ago in Paris.

The latest connection is Najem Alchraoui; a suspect in the Paris attacks who authorities now say they believe was one of the Brussels airport bombers.

Paris attacks suspect Salah Abdulsalam, who authorities captured after a gun battle last week, could be another link.

The Brussels attackers likely accelerated their plans when police discovered Abdulsalam’s hideout, investigators believe.

One of the apartments where he hid before his capture, located in the southern Brussels district of Forest, allegedly has ties to one of the Bakraoui brothers. A Belgian security source said Khalid El Bakraoui rented the apartment.