"The third man is on the run; he left his bag with the biggest bomb in it which exploded later because it was so unstable," Frederic Van Leeuw said, referring to the man in a hat and white coat in the CCTV images.
"This third person remains unidentified and is still being looked for," he said, adding that another man -- seen in black on the left of the footage -- was also unknown. The one in the middle was Ibrahim El Bakraoui, whose brother Khalid blew himself up on the Brussels metro, he said.