Nissan Motor Co expanded the North American recall of its top-selling Altima sedan to about 878,000 vehicles because a secondary hood latch may fail and cause the hood to fly up while the car is in motion, according to a company filing with U.S. safety regulators. Nissan has not yet found the root cause of the problem or how to fix it, and cannot definitely say whether the recall in North America will have to be expanded again.