Lagos, April 10 : At least fifteen people were killed when a bus and a truck collided head-on along a busy highway in the southern part of Nigeria, local traffic police have said. Bisi Kazeem, the national spokesperson for the Federal Road Safety Corps, disclosed this in a statement on Sunday and said that the accident took place at the Enugu-Port Harcourt expressway on Saturday night, Xinhua news agency reported. "The victims have been given mass burials. All obstructions have been cleared. The Enugu State Fire Service already extinguished the fire in the bus," he said. "The fatal crash is blameable on several factors, including fatigue, which must have made one of the drivers sleep on the wheels." While confirming no survivors from both vehicles, Kazeem warned motorists to desist from nighttime journeys to reduce fatalities from road crashes. Nigeria often sees deadly road accidents mainly caused by bad road conditions and reckless driving. /IANS