BRUSSELS—Belgian police investigating the Paris terrorist attacks have discovered an hours-long tape showing the home of a man working in Belgium’s nuclear sector, the country’s federal prosecutor said Wednesday.

The 10-hours-long video, discovered during a raid linked to the attacks, showed the exterior of a house, which investigators eventually discovered was the home of a man working in Belgium’s “nuclear world,” said Thierry Werts, a spokesman of the prosecutor’s office. He said a surveillance camera had been installed...