Brussels bombers Khalid and Ibrahim El Bakraoui planted a hidden camera to spy on a top nuclear researcher and hoped to build a "dirty bomb", according to reports.
An expert involved in a probe into Islamic State threats told NBC News that the brothers filmed more than 10 hours of footage of a senior researcher at a Belgian nuclear centre and his family.
The footage was seized during a Belgian raid in November, officials confirmed.
Former intelligence official Claude Moniquet, who was hired to investigate potential plots targeting the Europe's nuclear sector said: "The terrorist cell naively believed they could use him to penetrate a lab to obtain nuclear material to make a dirty bomb."
While the plot did not happen, he said the brothers then set up the camera to spy on the nuclear expert, confirmed as a "top researcher" by Belgium's Federal Agency for Nuclear Control.
New images show the scale of devastation at Brussels airport in the wake of last week's terror attacks which killed at least 35.
A report unearthed by ITV News shows the country was warned nine years ago that it was not equipped to deal with the growing issue.
Some communities have been made to feel ostracised within a society that was already divided.