CAIRO — The presidential campaign headquarters of Hosni Mubarak's last prime minister burst into flames Monday night as demonstrators protested against his confirmation as one of two candidates to advance to Egypt's runoff election.
If found to be arson, the fire would be the most destructive act of election-related violence since Mubarak's ouster as president last year. Interior Ministry officials said they had not determined the cause of the fire, though they arrested one person inside the building. They did not disclose the person's identity. The Associated Press reported eight arrests.
The fire broke out a few hours after the election commission confirmed that Ahmed Shafiq, the former prime minister and a former air force general, will face Mohammed Morsi of the Muslim Brotherhood in the runoff set for June 16-17 to choose Egypt's first freely elected president.
Several losing candidates had claimed electoral fraud, but outside observers said the election appeared valid, and the election commission rejected the appeals.
Shafiq's supporters express hope that he can restore order to Egypt while checking the power of the Muslim Brotherhood and other Islamists. His critics say they fear he will bring back the authoritarianism of the Mubarak government.
The recently elected Islamist-dominated Parliament passed a law barring top Mubarak officials like Shafiq from the presidency. But the election commission set it aside for review by the Supreme Constitutional Court. The commission said it would have the final word over the law's application even if the court approved it.
Groups of a few hundred or more people in Cairo, Alexandria and other cities on Monday evening protested Shafiq's candidacy. But his headquarters, in a villa in an affluent Cairo neighborhood, did not appear to have been the target of a protest.
The fire was put out within a few hours, and afterward, lights were on and campaign workers were visible inside the building. Outside, thousands of people gathered in the streets. No injuries were reported.
The electoral commission said Morsi, of the Muslim Brotherhood, won 5.8 million votes and Shafiq 5.5 million. The candidate who finished third, Hamdeen Sabahi, a socialist, received 4.8 million. Thirteen candidates were on last week's ballot. Turnout was 46 percent, much lower than in parliamentary elections.