Updated

A Chicago hospital reports that a 6-year-old boy who spent more than 3 hours underground after an Indiana sand dune collapsed on him was able to respond to "simple commands" upon arrival.

Comer Children's Hospital spokeswoman Lorna Wong said in a statement released Saturday that the boy is in critical condition and "has responded well to mechanical ventilation."

The boy was playing on the large dune at Indiana Dunes National Lakeshore on Friday when he dropped into a hole. Authorities say the dune collapsed in on him while his family was trying to save him and that he was buried for more than three hours under 11 feet of sand.

Michigan City, Ind., Fire Chief Ronnie Martin told WSBT-TV on Saturday that an air pocket saved the boy's life.