Explosions rocked the main airport terminal and a Metro station in Brussels, Belgium on Tuesday, a day after authorities said a new suspect in the Nov. 13, 2015 Paris terror attacks - possibly the bomb-maker - was likely loose in the city.

At least three dozen people were killed and more than 100 were injured by the blasts, at least one of which was likely caused by a suicide bomber.

More than 200 flights to Brussels were diverted or canceled after three explosions that authorities are calling terror attacks, according to the flight tracking service Flightradar24.

The Brussels airport was shut down and airport security has been tightened across Europe. The Brussels airport will be closed March 23.

Officials say three Mormon missionaries and a U.S. military family were injured in the attacks.

Zach Mouzoun, who arrived on a flight from Geneva about 10 minutes before the first blast, told BFM television that the second, louder explosion brought down ceilings and ruptured pipes, mixing water with victims' blood.

"It was atrocious. The ceilings collapsed," he said. "There was blood everywhere, injured people, bags everywhere."

"We were walking in the debris. It was a war scene," he said.

Video and photos from Brussels Airport, which is located in Zaventem, a suburb just northeast of the capital, showed windows of the main terminal blown out with smoke rising from the shattered panes.

French prime minister: "We are at war. We have been subjected for the last few months in Europe to acts of war."

Belgian media reported that gunshots were heard, and shouting in Arabic, before the explosions at the airport. CBS News could not independently verify those reports.

About an hour after the explosions at the airport, there was a blast at the Maelbeek Metro station in central Brussels, very near the U.S. Embassy and European Union headquarters. The Metro system was shut down. Emergency workers could be seen treating several injured people outside the metro station at Maelbeek.

The operator of Brussels' transport system said at least 15 people died in the Maelbeek attack.

"The Metro was leaving Maelbeek station for Schuman when there was a really loud explosion," Alexandre Brans, 32, told the AP as he wiped blood off his face. "It was panic everywhere. There were a lot of people in the Metro."

All flights in and out of Brussels Airport were cancelled, and all public transport in the Belgian capital was also shutdown. Eurostar trains in and out of Brussels from the rest of Europe were also cancelled Tuesday.

 Facebook has activated its "safety check" system to help people check on friends and loved ones in the aftermath of the attacks in Brussels.

The company says Tuesday the system was put in use within hours of the three explosions at the Brussels airport and a metro station.

It says the system can provide an easy way for people to mark themselves as "safe" after a major disaster or crisis so that people searching for them will know they are unharmed.

The system has been used recently to help people communicate after major floods and earthquakes as well as terrorist attacks.