Belgian federal prosecutors said on Friday that police had found traces of explosives, handmade belts and the fingerprint of a key Paris attacks fugitive during a raid on an apartment in Brussels on Dec. 10. Prosecutors, confirming a report in a Belgian newspaper, said that the apartment in the Brussels district of Schaerbeek had been rented under a false name that might have been used by a person already in custody related to the Paris attacks. The find adds to indications that the Nov. 13 shooting and suicide bomb attacks, in which 130 people were killed, were at least partially planned in Belgium.