By Leah Schnurr OTTAWA (Reuters) - A large sinkhole closed down part of the Canadian capital on Wednesday and forced the evacuation of businesses a few blocks from the national parliament, three weeks before Ottawa is due to host a summit of the leaders of Canada, Mexico and the United States. The sinkhole formed on a normally busy downtown street in an area that has been under construction for Ottawa's new light-rail transit (LRT) system. City officials said the cause of the sinkhole was not yet known but earlier gas and water leaks have been contained.
