(AP) - Construction workers' careless smoking is thetentative cause of a deadly blaze at a ground zero skyscraper thatkilled two firefighters, Mayor Michael Bloomberg said Monday. Bloomberg spoke after the Fire Department demoted three fireofficials and ordered more inspections and fire planning atbuildings throughout the city. The mayor said the fire was likely caused by "careless smokingby workers on the 14th floor" of the tower. City officials had said earlier that workers routinely tooksmoke breaks just outside the area where the fire occurred. Bloomberg said the department also failed to properly inspectthe building and ensure its safety. Saying that the city is obligedto reduce risks to firefighters wherever possible, "as a city Ithink it's to safe that we failed to do that."