Belgian authorities are seeking a second suspect over the attack on a metro train in Brussels in which one suicide bomber has already been confirmed dead, police sources told AFP on Thursday.
One source said a man with a large bag had been seen next to bomber Khalid El Bakraoui on CCTV footage at Maalbeek station, where officials say around 20 people were killed in Tuesday's attack.
Another source said Bakraoui was seen talking to a man who did not get into the train carriage with him.
"Investigators want to know who this man is," one source said.
A huge manhunt is already underway for a third attacker at Brussels airport, who was seen on security footage with Khalid El Bakraoui's brother Ibrahim and a man identified as Najim Laachraoui, but whose bomb did not go off.