"There was an explosion tonight at a hotel in the Kabala West area of the city," said police spokesman Aminu Lawal. "We don't know what caused the explosion yet or if it was a deliberate attack."
There was conflicting information on casualties, with a spokesman for the national emergency management agency saying there were initial unconfirmed reports of two people being caught up in the blast.
Vice President Namadi Sambo is from the state of Kaduna, where the city of the same name is located.
Two blasts had earlier gone off in the northeastern city of Maiduguri — one on Friday night and one yesterday morning — but no casualties were reported.
Voting was generally calm yesterday in most of the country despite the blasts and a number of other incidents as Africa's most populous nation sought to hold its cleanest polls for president in nearly two decades.
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