(CNN) — For investigators, there’s no time to mourn.
The hunt is on to find those responsible for a series of blasts in Brussels, Belgium, that killed at least 30 people and wounded 230.
The loved ones of those killed will grieve in the coming days. They will move on without fathers, mothers, husbands, wives and children.
But investigators will do what they do: dig.
They will try to ascertain clues based on the explosives that struck the airport and a metro station in Maelbeek. They’ll hunt for the one remaining suspect that they think is alive, digging up information and attempting to untangle the network used to plan the attack. And they’ll use this information to try to stop any future attacks that may be in the works.
Three suspects, two explosions and a taxi driver
One of the first major breaks in the investigation appears to have come from a taxi driver.
Just hours after the explosions, Belgian authorities released a photo from airport security that showed three men — two in black and one in lighter clothes, wearing a hat.
Police identified brothers Khalid and Brahim El Bakraoui as the suspected suicide bombers at Brussels’ international airport, state broadcaster RTBF reported. The pair were known to police, but for organized crime, not for acts of terrorism.
Video shows the men exiting a taxi and moving through the airport, according to two U.S. officials.
The two in darker clothes are believed to be suicide bombers who died in the explosions in the airport’s departure lounge, according to Belgian federal prosecutor Frederic Van Leeuw.
But investigators believe the man in light-colored clothing planted a bomb at the airport, then left — a move that appeared to be planned, the two U.S. officials said.
Authorities are calling him a wanted man and asked for the public’s help tracking him down.
“It’s Salah Abdeslam all over again,” Dirk Coosemans, a reporter at Belgian newspaper Het Nieuwsblad, told CNN. “This one was there to be a suicide terrorist, and he didn’t do it.”
Belgian media also reported a Kalashnikov assault rifle was found in the departure hall of the Zaventem airport.
Fortunately, a taxi driver called police shortly after the photo was released and said he believed that he drove the trio to the airport.
The driver told authorities that his passengers would not allow him to unload the suitcases from the cab. He also led investigators to the location where he picked the three of them up.
Schaerbeek
That information prompted authorities to raid a residence after the attacks, the officials said.
Investigators found a nail bomb, chemical products and an ISIS flag during a house search in the northeast Brussels neighborhood of Schaerbeek, Belgium’s federal prosecutor said in a statement.
Forensic teams are now scouring an apartment building in that neighborhood and have been seen carrying out bags of evidence, according to CNN’s Frederik Pleitgen, who was reporting from just outside the building.
Their work continued into the night.
Putting the pieces back together
Investigators are looking at whether one of the airport explosions may have been caused by a bomb inside a suitcase, while the other was a suicide bombing, according to a U.S. official briefed on early evidence from the investigation.
Determining what type of explosives were used will be crucial, according to CNN National Security Analyst Peter Bergen.
French prosecutors have said that the bombs used in the November Paris attacks were made from triacetone triperoxide, or TATP.
If the same type of bombs were used in Paris and Brussels, that would be a key clue linking the two attacks.
“Such bombs have been a signature of jihadist terrorists in the West for more than a decade because the materials are so easy to acquire, unlike military-grade explosives, which are tightly controlled in much of the West,” Bergen said.
TATP-based bombs require technical know-how and bulk purchases of hydrogen peroxide or hair bleach. That helps authorities winnow down potential bomb-making suspects, because making the explosives can sometimes bleach hair. So authorities can identify bomb-makers in part by recognizing unusually-bleached hair or asking sellers to report any suspiciously large purchases of hydrogen peroxide.
Dearth of Maelbeek information
While authorities have been able to move quickly on intelligence from the airport attacks, very little has been publicly revealed about the bombing at the Maelbeek metro station.
Coosemans, the Het Nieuwsblad reporter, says that’s because there isn’t as much surveillance there compared to the airport.
“We just know less about the Maelbeek attack because we don’t have pictures there,” he told CNN. “The police know less about Maelbeek.”
Unraveling the network
Two senior U.S. officials told CNN they believe the Belgium attack is tied to the same network as terror suspect Salah Abdeslam (ISIS has claimed responsibility for the attack.)
And the “working assumption” in Belgium is that the attackers came from the network behind the Paris attack, Belgian security sources said. However, they cautioned it is very early in the latest investigation.
The identities of the three airport suspects aren’t clear to U.S. authorities, either because Belgian authorities haven’t completed identification or haven’t shared that information with counterterrorism officials in the U.S., the officials said.
Going forward, intelligence sharing will be very important, says Steve Moore, a CNN law enforcement contributor.
“They obviously have some information. They don’t know if they’re looking at one cell or a series of cells. And so now it’s time to get all around at the same table and exchange information,” he said. “If you can get them all to use the same currency, I cannot believe that you can’t get them all to share intelligence.”
