Masked special police, backed by helicopters, searched a western Serbian town on Sunday as part of a stepped up hunt for UN war crimes fugitive Ratko Mladic, witnesses and media said. The Beta news agency reported that police arrested two people in a three-hour search of the town of Valjevo, about 80 kilometers (50 miles) southwest of Belgrade, where the Bosnian Serb wartime commander is known to have lived in the past. "Something did happen," a police official in Valjevo, told the Associated Press on condition of anonymity because he is not entitled to talk to the press. "The special police came with helicopters, but it had nothing to do with us." The Valjevo officer could not confirm the arrests reported by the Beta news agency. There was also no immediate confirmation of the action from Serbian police in Belgrade.