Smoke still lingered the day after flames engulfed a warehouse housing electoral materials on Wednesday in Kinshasa, the officials said. The ruined ballot machines were among 10,000 due to be used in the December 23 vote, Congo's electoral commission chief, Corneille Nangaa, said. Police are working to determine the fire's cause, according to local reports.Voting materials from other parts of the country will be sent to Kinshasa, and election preparations will continue as planned, the electoral body said. An opposition coalition that has objected to the use of voting machines called for an investigation into the warehouse fire. The coalition, led presidential candidate by Martin Fayulu, alleges the machines could aid vote-rigging.Voters in Congo head to the polls following a violent campaign season to pick a successor to President Joseph Kabila, who has ruled since 2001.Kabila took over after his father, Laurent Kabila, was assassinated and has since maintained a fierce grip on the nation. His second term ended in 2016, but he refused to step down and tried to change the constitution to extend his tenure.Kabila has backed his former interior minister, Emmanuel Ramazani Shadary, to succeed him.