Police have arrested four more suspects linked to a high-profile knifepoint robbery in Hong Kong following a joint cross-border operation, though the stolen gold bars remain missing. The force shared an update on its investigations on Monday, after a 36-year-old local man, carrying a backpack loaded with six gold bars weighing about 6kg (13.2lbs) and valued at HK$7 million (US$893,200), was ambushed by three knife-wielding assailants at Hong Kong International Airport’s car park 3 early on...