At least 31 people have died and 270 have been injured.
Reports about the victims are trickling in. Several memorials have been set up to pay tribute those who were killed.
Belgium remains at Level 4 terror threat.
Following the attacks, Belgian leaders raised the threat level to four -- the highest in Belgium.
Authorities arrested one person following a massive manhunt. But they have released him.
Belgian media initially reported that the person arrested Wednesday was 24-year-old Najim Laachraoui, whom European security officials have described as a suspected Islamic State bomb maker. But those reports were later retracted. Laachraoui is still being sought.
Police say the brothers responsible for the Brussels attack are connected to a key suspect in the Paris attacks.
The brothers had connections to Salah Abdeslam, a suspect from last year’s attacks in Paris who was arrested in Brussels. Abdeslam's fingerprints were found in the apartment rented by one of the Brussels bombers.
The Islamic State has claimed responsibility.
The extremist group posted a statement on a website asserting its responsibility within hours of the attacks.