CAIRO — Egypt on Saturday said there is a 90 percent chance that hidden chambers will be found within King Tutankhamun’s tomb, based on the preliminary results of a new exploration of the 3,300-year-old mausoleum. Researchers say the discovery of a new chamber could shine new light on one of ancient Egypt’s most turbulent times, and one prominent researcher has theorized that the remains of Queen Nefertiti might be inside. Egypt began the search for the hidden chamber last week.