CHICAGO (AP) _  The condition of a 6-year-old boy rescued after being buried by 11 feet of sand at an Indiana dune has been upgraded.
 
  Comer Children's Hospital in Chicago announced Tuesday that the condition of Nathan Woessner  of Sterling, Ill., was upgraded to serious Thursday. He had been in critical condition since being rescued from the Indiana Dunes National Lakeshore on Friday. 
 
  Doctors have said he is expected to make a full neurological recovery, though he may suffer lingering lung problems. 
 
  National Park Service Ranger Bruce Rowe says geological equipment will be brought in over the coming weeks to try to determine how the boy became buried in the dune. He says that until officials know more, the dune known as Mount Baldy and the surrounding area will remain closed.