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Terrorist attacks in Brussels: What we know right now

The situation on the ground in Belgium continues to evolve, but here is what we know for sure as of right now.

The city of Brussels remained on high alert Wednesday after explosions the previous morning rocked the local airport and subway, killing at least 31 people and injuring hundreds more in what appears to be a coordinated terrorist attack. Residents are being told to stay indoors as the country's transportation system remains shutdown.

The situation on the ground in Belgium continues to evolve, but here is what we know for sure as of right now:

Timeline of the attack: The first blast hit at 8 a.m. in Brussels (3 a.m. EST in the U.S.) and was quickly followed by a second explosion. The governor of the Flemish Brabant province has said three bombs were used in the airport attack, but one did not detonate. The explosives reportedly contained nails, and victims were treated at local hospitals are suffering from burns, deep cuts and fractures, caused by flying metal objects. Less than hour later, an explosion hit a crowded subway system during rush hour.

The victims hurt: According to the mayor of Brussels, 20 of the victims were killed at an explosion at the Maalbeek metro station and the Belgian ministry of health believes that at least 11 more were killed at the airport. First responders in the country added that more than 200 were also wounded in the attacks. And we now know that at least three of the wounded were American Mormon missionaries — Richard Norby, 66; Joseph Empey, 20; and Mason Wells, 19 — all of whom are in currently critical condition, but did not suffer life-threatening injuries. In addition, an American service member and four of his family members were also hurt at the airport, but the injuries were not believed to be life threatening, NBC News reported.

ISIS has claimed responsibility: After initial silence, the terrorist organization ISIS eventually issued a statement later on Tuesday afternoon via their own news agency Amaq, taking responsibility for the attacks — U.S. counterterrorism authorities have said the claim appears genuine. Authorities suspected ISIS had a hand in the bombings early on, and this represents yet another troubling example of their increasingly organized efforts to spread fear throughout Europe. Belgian media reported that authorities conducted a raid in the Schaerbeek area of Brussels, where they discovered explosives and an ISIS flag. 

The search is on for suspects: Belgian police are currently investigating three suspects who appeared in a photograph taken at the Brussels airport Tuesday morning. They all appear to be pushing luggage carts and authorities believe that one of the men, perhaps the individual on the right pictured in a hat and white jacket, may have survived the purported suicide bombing and fled the scene. Belgian police tweeted the photo with the question: “Who recognizes this man?”

Early on Wednesday, the three men were identified. The two who died in the suicide bombing on Tuesday were bothers, Khalid, 27, and Ibrahim El Bakraoui, 30, with links to at least one of the Paris attackers. Both brothers had been on Beligian authorities' radar and had been convicted of violent crimes in the past. Ibrahim served 9 years in prison for shooting at police with an assault rifle during a robbery. Meanwhile, Khalid has been arrested for possession of Kalashnikovs and served five years in prison for "carjackings."

According to RTBF and the Belga news agency, he had lived in an apartment in the now infamous Forest neighborhood and Brussels where authorities engaged in a shootout with suspects during a raid connected to the Paris terror attacks last November. Reportedly an ISIS flag and extremist manual were among the items recovered at that scene.

Meanwhile, "the man in the hat" has been identified as Najim Laachraoui, 24, who, according to authorities, traveled with Paris attack suspect Salah Abdeslam. He used the alias "Soufiane Kayal" during a 2013 trio to Syria. Currently there is a massive manhunt under way for Laachraoui who is believed to have survived the suicide bombings of Tuesday morning. NBC News has confirmed that three suitcase bombs were involved in the airport attack, but one of the three was not detonated until authorities arrived on the scene. According to BFM, the taxi driver who took the three suspects to the airport took note of the significant weight of their luggage and said they demurred when he tried to help them with it.

On Wednesday morning, authorities confirmed that further raids have resulted in at least one arrest, but there has been no word on whether they apprehended any more suspects.

Paris attacker may be motivation: Some have already been speculating that Tuesday’s attacks were a coordinated response to the capture of Paris bombing suspect Salah Abdeslam, who was apprehended, along with four others, in a raid in Brussels this past Friday. Authorities gained intel on Abdeslam’s whereabouts after conducting a routine search of a Brussels apartment that led to a gunfight with an Algerian ISIS member Mohamed Belkaid, believed to have been an accomplice of Abdeslam. Belgium’s foreign minister has said that Abdeslam had plotted to “restart something” in Brussels — which may have been borne out by the large cache of weapons discovered during his arrest. Meanwhile, on Monday, Najim Laachraoui, 24, was named as another potential suspect in the Paris attacks last November. Still, no official link between the attacks in Brussels and Paris has been confirmed.

World leaders, presidential candidates respond: The prime minister of Belgium has called Tuesday a “dark moment for our country,” and President Obama has called on the world to “unite” in the wake of the attacks.

In addition, several of the 2016 presidential contenders seized onto the tragedy as an opportunity to launch rhetorical bombs at the White House. On NBC’s “TODAY” Donald Trump made the case that he was in the “camp” of advocating for torture to obtain information on today’s attack and he ridiculed the president on social media for continuing his diplomatic trip to Cuba amid the crisis. After several tweets emphasizing his own prowess, Trump later in the afternoon offered "prayers" for the victims. Meanwhile, his chief rival Sen. Ted Cruz complained that “political correctness” was inhibiting the war on terror, and repeated a common attack on Obama over his avoidance of the term “radical Islam.” He also advocated for "patrols" of Muslim neighborhoods in the U.S. For his part, Gov. John Kasich took shots at the president for attending a baseball game.

Democratic presidential front-runner and former secretary of state Hillary Clinton pushed back at Trump's proposal to strengthen borders and said that "even if we were to build a tall wall around the entire continental United States, the internet would still get over it." Her rival Sen. Bernie Sanders also responded to his Republican rivals' proposals and said that conducting surveillance of Muslim neighborhoods would be wrong and unconstitutional. "We are not fighting a religion," he added.

—NBC News provided reporting for this article.