Breaking news update

Brussels, Belguim-A Belgian subway official says there are 15 dead, 55 injured in the subway station attack in Brussels.   Spokesman Guy Sablon gave the toll to The Associated Press after two explosions hit the Brussels airport on Tuesday morning and a third hit the city's Maelbeek metro station.  The death toll at the airport is reported to be 13.  

Breaking news update, posted at 6:01 a.m. ET

Brussels, Belgium (CNN)At least 23 people have been killed in three explosions in Brussels, Belgium, according to Belgian media.

Ten were killed at a subway station, according to two Belgian broadcasters, and at least 13 were killed at the airport, according to public broadcaster VRT.

Breaking news update, posted at 4:30 a.m. ET

Brussels, Belgium (CNN)Several people were killed in two explosions that occurred at an airport in Brussels, Belgium, on Tuesday, Reuters reports, citing the country's public broadcaster, RTBF.

Brussels, Belgium (CNN)Two explosions occurred at the airport Brussels, Belgium on Tuesday.

Federal police at the airport at Zaventem told CNN that "there has been an explosion" and "something has happened."

Dozens of people have been taken on stretchers out of the airport, according to eyewitnesses.

The Brussels airport tweeted that there have been two explosions and said that "the building" is being evacuated. They also said all airport operations have been suspended and asked those nearby to remain calm.Anthony Barrett said he heard something at about 8 a.m. local time from his hotel across from the terminal building.

"When I opened the curtains and looked out, I could see people fleeing," he told CNN.

He said he's seen about 19 or 20 stretchers carrying people so far. Luggage trollies were also being used to transport the wounded.

"It's clearly a very serious incident," he said.

It's unclear what caused the explosions, or if they're related to terrorism.

The airport is currently being evacuated and a disaster plan has been initiated, according to CNN affiliate RTL. Passengers have been directed to the runways.

Witnesses told RTL at least one of the two explosions took place in the airport's departure hall.The incident comes after Salah Abdeslam, a man who authorities say was involved in the Paris terror attacks last year, was arrested in the Brussels suburb of Molenbeek on Friday.