Belgian prosecutors have launched a public appeal for any information on the “man in hat” suspect in the Brussels Airport suicide bombings that killed 16 people.

Belgian Federal Prosecutor Eric Van der Sypt said Thursday that authorities were especially appealing to people who might have filmed or photographed the man. He was seen with two suicide bombers who died in the March 22 attacks. A subsequent explosion at Brussels’ Maelbeek subway station killed another 16 people the same day.

Photos released by the prosecutors showed him leaving the airport on foot, walking to the nearby town of Zaventem and then into Brussels, where all traces of him were reportedly lost.

The suspect also wore a white jacket but discarded it at some point, prosecutors said.

(AP)