The third suspect in the Brussels attacks is still on the run, Belgian Federal Prosecutor Frederick Van Leeuw reportedly said Wednesday. The attack on the Zaventem Airport and a metro at Maalbeek station killed 31 people and injured 270 others, Leeuw added.

He said that the toll is expected to rise as some of the injured victims are in critical condition, the Guardian reported.

The prosecutor confirmed that Ibrahim el-Bakraoui was the first person to blow himself up inside the airport. The second suspect who was behind the second bomb blast at the airport has not been identified, Leeuw said at a news conference Wednesday.

The prosecutor did not identify the third suspect who was seen alongside the two suicide bombers in the airport's CCTV footage. His name has, however, been reported as Najim Laachraoui by media. The Belgian Police is on the lookout for the third man seen in a white dress and a hat in the footage.

Leeuw identified the man behind the attack on a metro at the Maalbeek metro station as Khalid el-Bakraoui, Ibrahim's brother. Khalid exploded himself inside the train when it was still inside the station, the prosecutor said. 

Both Khalid and Ibrahim has "very heavy police files" on other crimes not related to the Brussels attacks. The Belgian Police conducted a search of an apartment in Schaerbeek after the attacks. They found a note by Ibrahim in a laptop that they seized from the apartment. Ibrahim knew the police was searching for him and he did not want to be arrested, the note read.

The police in Schaerbeek questioned two people Tuesday. One of them was set free after thorough interrogation, while the other was still being questioned by the police, Leeuw said.

The attacks in Brussels took place days after the Belgian police arrested Salah Abdeslam, the suspect in the Nov. 13 Paris attacks in which at least 130 people were killed and several others injured. The Islamic State group claimed responsibility for the Brussels attacks.