Japanese police said Sunday that an unknown number of vehicles were ablaze inside a motorway tunnel after it caved in 80 kilometres (50 miles) west of Tokyo. \"We don\'t know exactly how many vehicles are on fire,\" an official at the local expressway traffic police unit told AFP by telephone. He said the accident occurred on the Tokyo-bound lanes inside the Sasago tunnel on the Chuo Expressway at around 8:00 am (2300 GMT Saturday).