The footage shows the man wearing a hat and white jacket pushing a trolley with a large bag through the departure hall, next to suicide bombers Ibrahim El Bakraoui and Najim Laachraoui.
"It's a new video which had not previously been released," a spokesman for the federal prosecutor's office told AFP.
A police notice issued with the video - still images from which have previously been released - said that officers "want to identify this man".
Cheffou is however not cooperating with investigators, the source said.
Belgian officials earlier raised the toll from coordinated suicide attacks on Zaventem airport and a metro station in the centre of the city to 35.