Cleanup continues on the site of a spill of emulsion, a mixture of bitumen, water and sand, at a feeder pipeline corridor near Nexen Energy's Long Lake oilsands facility, south of Fort McMurray, Alberta July 22, 2015. A Nexen Energy senior executive said on Wednesday it will likely take months to find the root cause of an oil sands pipeline leak in northern Alberta that was one of North America's largest-ever oil-related spills on land. REUTERS/Mike DeSouza