The bus was on its way from Aizawl to Champhai, the district headquarters town in Champhai district, on the Indo-Myanmar border.
The officials in Champhai police station said the driver of the bus, who was also severely injured, could not negotiate his way as the area was shrouded in thick mist around 2 in the morning.
Police contingents from Champhai, accompanied by the Young Mizo Association (YMA) volunteers, rushed to the site of the accident and launched a rescue operation.
The injured were sent to the civil hospitals in Aizawl and Champhai. A medical team was also pressed into service. Among the dead, three were non-Mizos.
One of the dead has been identified as Bijon Ghosh, a vegetable trader in Dholai in Cachar district. Police sources in Dholai said 45-year-old Ghosh had gone to Mizoram that night to fetch consignments of chillies. He was cremated in Dholai yesterday.