US and Mexican officials say they have discovered an elaborate tunnel used by criminals to smuggle drugs across the California-Mexico border. The tunnel, which is more than 500m long (1,640ft), is equipped with a rail system, ventilation and lighting. Inside, police found more than 20 tonnes of marijuana. They said the tunnel connected a warehouse in Otay Mesa with one in Tijuana in Mexico, the main gateway for drugs entering California. Police say drug traffickers build the tunnels to bypass ever more stringent controls aimed at curtailing the cross-border trade in illegal drugs and guns. In 2006, police discovered a 731m (2,400ft) tunnel, the longest found so far, also linking Otay Mesa with Tijuana. Source: BBC