Suspects were rounded up across Europe in the wake of Tuesday’s terror attacks in Brussels that are now known to have killed 31, including two Americans. The arrests come amid warnings that two of the suicide bombers, who have been linked to ISIS, were scoping out Belgian nuclear facilities in the hope of creating a “dirty bomb” that would have scattered radioactive material over a wide area. Seven men have now been arrested in Belgium in connection with the bombings. Local reports suggest that the man wearing a light hat in the widely distributed CCTV pictures from Brussels Airport, shown walking alongside two suicide bombers pushing luggage carts, is among those who have been detained. Belgian officials also issued a wanted notice for 28-year-old Syrian Naim al-Hamed, whom police describe as “very dangerous.” He was also suspected of involvement in the Nov. 13 attacks in Paris that killed 130 people. Meanwhile, new details emerged of the suspect who was arrested in Paris on Thursday. French Interior Minister Bernard Cazeneuve said in a televised address that the raid helped “foil a plot in France that was at an advanced stage.” Officials identified the man as Reda Kriket, 34, who was sentenced in absentia to 10 years in prison in Belgium last July for recruiting Islamist fighters to go to Syria.