US authorities are looking into whether al-Qaeda in Iraq leader Abu Musab al-Zarqawi was killed in a gunfight in Mosul, a US official says. But a White House spokesman said al-Zarqawi's death was "highly unlikely." "Efforts are under way to determine whether Zarqawi wasamong those killed," the US official, in Washington said, speaking on condition of anonymity. White House spokesman Trent Duffy, travelling with US President George W Bush in Asia, said the report was "highly unlikely and not credible." US forces had sealed off the house in the northern city of Mosul where eight suspected al-Qaeda members died in...