Two of the suicide bombers who carried out attacks in Brussels on Tuesday have been named as brothers Khalid and Brahim el-Bakraoui, Belgian nationals.
The federal prosecutor said Brahim was part of the attack at Zaventem airport that killed 11 people. Khalid struck at the Maelbeek metro, where 20 people died. In all 260 people were injured.
Police are still hunting another man seen in an airport CCTV image.
Belgium is observing three days of national mourning.
The nation held a minute's silence at midday (11:00 GMT) on Wednesday.
So-called Islamic State (IS) has said it was behind the attacks and warned that more would follow.
On Wednesday, anti-terror police also carried out a raid in the Anderlecht area of the city, making one arrest.
The federal prosecutor, Frederic van Leeuw, denied earlier media reports that the man was wanted jihadist Najim Laachraoui. The arrested man's identity has not been released.
Mr van Leeuw said the two brothers were known to police and had criminal records but these were not related to terrorism. They were identified by DNA records.
He said Brahim el-Bakraoui had left a note saying that people were looking for him everywhere and that if he gave himself up he would end up in a cell.
The RBTF broadcaster, quoting a police source, said that Khalid el-Bakraoui, 27, had used a false name to rent the flat in the Forest area of the Belgian capital where police killed a gunman in a shootout last week.
It was during that raid that police found a fingerprint of Salah Abdeslam, the main suspect in the Paris terror attacks of 13 November.
He was arrested in a raid in Brussels last Friday and is due to appear before a pre-trial court on Wednesday.
Khalid el-Bakraoui appears on the Interpol website. It says that he is being sought for terrorist activities.
RTBF said Khalid was jailed in 2011 for carjacking while Brahim, 30, was jailed in October 2010 for firing at police.
Brahim el-Bakraoui is in the middle of the widely circulated CCTV image taken at Zaventem airport, Mr van Leeuw confirmed.
The man on the left is believed to have died at the airport but has not been identified.
The man on the right has not been identified and is still being sought, Mr van Leeuw said.
He said that this man had a bag of detonators that were left behind and which were later exploded without harming anyone. No other weapons were found at the airport.
Belgian newspaper La Derniere Heure had earlier identified this man as Laachraoui. He was named earlier in the week by police as a wanted accomplice of Abdeslam.
Analysts say Laachraoui is believed to be a key bomb maker, and French media say he also played a major role in the terror attacks in Paris.
Some Belgian media reported on Wednesday that he was the man arrested in Anderlecht but this report has been withdrawn.