The National Weather Service said that a portion of the tornado that touched down in northern Kentucky was stronger than first thought.The NWS upgraded the tornado that struck Piner to an EF4 on Friday afternoon, one week after it tore through the area killing four people.A final review of images from the tornado and information from the Kenton County Sheriff's Office indicated that the tornado reached speeds up to 175 mph from the west side of Interstate 75 to the north end of Old Lexington Pike.All four of the fatalities in Kenton County occurred within the area where the tornado was its strongest, the NWS said.The NWS said that while five single-family homes were destroyed to the foundations in that particular area, two of the homes met the criteria for an EF4 tornado.In addition, at least two vehicles were carried by the storm, one of which was carried 1,800 feet, and trees in the area were stripped of nearly all the branches and much of their bark.The tornado cut a path from Crittenden, through Piner and into Morning View. Kenton and Pendleton counties have been declared federal disaster areas because of the tornadoes.