Only the brick shell and chimney remain intact Monday at the old Boone School. Air traffic controllers at the Salt Lake International Airport spotted a blaze Sunday night that destroyed the abandoned school building at 749 S. Gladiola (2970 West). Controllers reported the fire at 8:53 p.m. Firefighters did not enter the small school building when they arrived because the interior, filled with burning rubble, was engulfed in flames, a dispatcher said. Firefighters battled the blaze from outside the building to ensure the flames did not spread to surrounding fields. Investigators Monday sifted through the charred interior searching for the cause of the fire, which was labeled suspicious. The Granite School District operated the school, which last held classes during the 1952-53 school year. The building was sold later in 1953 to the Salt Lake City School District and was used for storage until it was sold to a private party in 1972, according to Salt Lake district records.