The federal prosecutor's office said in a statement on Wednesday that an "investigation is actively ongoing."

Belgian media reported that several hours of video was filmed near the home of a man thought to be a senior official at the Mol nuclear waste facility in the Flanders region. The house of the unidentified man was apparently filmed from a nearby wood.

Prosecutors declined to confirm that information or provide details.

Security services have long feared that extremists might get their hands on radioactive material.

It comes as a cloud hangs over some Belgium's nuclear plants after a number of unplanned shutdowns.