LAGOS, Nigeria (AP) – A truck bomb aimed at electoral commission headquarters ran into obstructions and failed to explode hours before the start of Nigeria’s presidential vote, the national police chief said Saturday.

Police Inspector General Sunday Ehindero said that the attacker pointed the truck loaded with fuel and gas cylinders toward the headquarters and placed a rock on the accelerator before jumping from the vehicle, which was stopped by obstructions before reaching the building. A suspect was apprehended in the pre-dawn attempted attack, he said on national television.

At least 49 people have been killed since chaotic state elections last weekend and many more have been reported dead in earlier political violence. In a national address Friday, President Olusegun Obasanjo pleaded with his citizens to vote peacefully.

If successful, Saturday’s election will set up a transfer of power between elected civilian leaders for the first time since Nigeria gained independence from Britain in 1960. Other attempts have been overturned by annulments or military coups.