BRUSSELS — As police hunted for the surviving Brussels bomber, evidence mounted Wednesday that the same Islamic State cell carried out the attacks in both Paris and Brussels, and that the militants may have launched this week's slaughter in haste because they feared authorities were closing in on them.
On a day of mourning across Belgium following Tuesday's bombings of the Brussels airport and subway that killed 31 people and wounded more than 270, new information emerged about the four attackers:
• European security officials said one of the suicide bombers was Najim Laachraoui, a Moroccan-born Belgian whom police have hunted as the suspected bombmaker in the Nov. 13 attacks on Paris by the Islamic State that killed 130 people.
• The other two suicide bombers were Belgian-born brothers, Ibrahim El Bakraoui, and his younger brother, Khalid, both known to the police as common criminals, not anti-Western radicals.
• Turkish President Recep Tayyip Erdogan said Ibrahim El Bakraoui was caught in June 2015 near Turkey's border with Syria and deported, at his own request, to the Netherlands, with Ankara warning Dutch and Belgian officials that he was a "foreign terrorist fighter." But other Turkish officials said he was released from Dutch custody due to lack of evidence of involvement in extremism.
Details of the investigation from chief prosecutor Frederic Van Leeuw pointed to a rising sense of panic among the three bombers who blew themselves up. An unidentified fourth man who was shown in airport video surveillance footage remains at large after Van Leeuw said his suitcase bomb failed to detonate properly. Authorities say he was the man in a light jacket and hat on the far right of the video footage.
Van Leeuw said the bomb did partially explode after police had already evacuated the terminal, injuring nobody.
The prosecutor said a laptop seized from a garbage can on a street outside the brothers' last known address contained a message purportedly from Ibrahim El Bakraoui that indicated he was expecting to be arrested imminently following Friday's capture in Brussels of the suspected ringleader of the Paris attacks, Salah Abdeslam.
"I don't know what to do, I'm in a hurry, people are looking for me everywhere," Van Leeuw quoted the message as saying. "If I give myself up I'll end up in a cell next to him," — an apparent reference to the just-arrested Abdeslam.
Police were drawn to the brothers' apartment Tuesday night thanks to a tip from a taxi driver who had unwittingly delivered them to the airport, Van Leeuw said. Inside the northeast Brussels residence they found an apparent bomb-making factory, including 15 kilograms (33 pounds) of homemade explosives and nails for use as shrapnel.
Neighbors told The Associated Press they had no idea of the brothers' activities and barely saw them until the taxi collected them and their visibly heavy bags Tuesday morning.
One neighbor, who was willing to give only his first name of Erdine, said he was about to drive his son to school when he saw the two men carrying their bags out of the building.
"The taxi driver tried to get the luggage. And the other guy reached for it like he was saying: No, I'll take it," the neighbor said.
At the core of the Belgian investigation is a photo taken from the airport's surveillance cameras showing three attackers walking side by side as they push luggage carts. Van Leeuw said the middle figure has been identified as Ibrahim El Bakraoui, while the two men flanking him remained unidentified.
But two security officials told the AP that Laachraoui's DNA was verified as that of one of Tuesday's suicide bombers after samples were taken from remains found at the airport. One European official and one French police official spoke on condition of anonymity because they weren't authorized to divulge details of the Belgian investigation. Both officials were briefed on the investigation.
Belgian officials have not publicly linked any of the remains to Laachraoui; nor have they said he was involved in the Brussels attack.
Since prosecutors said Khalid El Bakraoui was killed in the subway bombing, that would make Laachraoui the remaining unidentified figure on the far left of the airport video footage.
Belgian authorities have been looking for Laachraoui since last week, suspecting him of being an accomplice to Abdeslam, who was arrested Friday in the Brussels neighborhood where he grew up.
Laachraoui is believed to have made the suicide vests used in Paris, a French police official told the AP, adding that Laachraoui's DNA was found on all of the vests as well as in a Brussels apartment where they were made. The official spoke on condition of anonymity because he wasn't authorized to discuss an ongoing investigation. Seven of the Paris attackers blew themselves up or were slain by police.
French and Belgian authorities have said the network behind the Paris attacks was much larger than initially thought — and developments this week suggest the same group could have staged the violence both in Paris and Brussels.
"It's the same team," said a French senator, Nathalie Goulet, who is co-leader of a parliamentary commission on studying jihadi networks.
She said Abdeslam should have had little difficulty organizing more recruits following his November escape from France.
"He probably had 10 more at hand who would be ready to do the same thing tomorrow morning," she said, describing his Brussels acolytes as "like a scout troop ... a troop of death."
A Belgian official working on the investigation told AP it is a "plausible hypothesis" that Abdeslam was helping to organize the Brussels attack. The official spoke on condition of anonymity because he was not authorized to discuss the investigation.
The comments by the Turkish president that Ibrahim El Bakraoui was determined by his country to be a militant fighter and then deported to Europe could raise embarrassing questions for Western security officials.
But a Turkish official who spoke on condition of anonymity because he wasn't authorized to speak publicly said the bomber was allowed to go free because Belgian authorities could not establish any ties to extremism.
Belgian Justice Minister Koen Geens said authorities would have no reason to have detained Ibrahim El Bakraoui last year as an Islamic State suspect because he was "not known for terrorist acts but as a common law criminal who was on conditional release."
Ibrahim El Bakraoui, 29, received a nine-year prison sentence in 2010 for shooting at police following an attempted robbery of a currency exchange, while Khalid El Bakraoui, 27, served a brief sentence for attempted carjacking.
Belgian state broadcaster RTBF, citing sources it did not identify, said Khalid El Bakraoui had rented an apartment that police raided last week in an operation that directly led to Abdeslam's arrest at another apartment just a few streets away from his parents' home.
Wednesday was the first of three official days of mourning, and thousands gathered at the Place de la Bourse, a central square in Brussels, to remember the victims.
"Long live Belgium!" some declared.
The attacks badly rattled Brussels' transportation links. Several subway stations in the city center and at the airport remained closed. Officials at the airport, which typically handles 600 flights daily, said it would remain shut down until at least Saturday.
Many of the dead remained unidentified, partly because of the severity of devastation caused by the nail-packed bombs detonated in crowds. Eleven people were confirmed dead at the airport, 20 inside the Maelbeek subway station.
In a second claim of responsibility Wednesday, the Islamic State group warned of further attacks and what it called "dark days" for countries involved in attacking IS positions in Syria and Iraq.
French Prime Minister Manuel Valls said major cultural and sports events should not be postponed for fear of attack. He said that includes the monthlong European soccer tournament being staged throughout France in June.
A planned soccer match between Belgium and Portugal, originally scheduled for March 29 in Brussels, was moved to Portugal.
Associated Press reporters Raphael Satter, Danica Kirka and Lorne Cook in Brussels, Lori Hinnant and Elaine Ganley in Paris, Suzan Fraser in Ankara, Turkey, Jill Lawless in London and Shawn Pogatchnik in Dublin contributed to this report.