Eleven people, including a pregnant woman, an infant and an aged woman, a police officer and seven others died in a crash on Iseyin-Saaki road in Oyo.
But police spokesman Olugbenga Fadeyi in his confirmation of the accident put the death toll at four.
The accident occurred when a Saki-bound 18-seater bus ran into a stationary truck at around 9pm.
It was suspected the driver of the bus slept off on the wheel, and the vehicle subsequently veered off its lane to collide with the stationary truck.
A total 11 of the 13 passengers died.
The Oyo state Sector Commander of the Federal Road Safety Corps (FRSC) Mrs Uche Chukwurah, when contacted, said the command was not in the picture.
She said since the said accident occurred by night, it was not reported to the command.