The boy, whose survival was described as a "miracle" by a local coroner, remained in critical condition Saturday at Comer Children's Hospital and has responded well to being on a ventilator, hospital spokeswoman Lorna Wong said in a statement.
The hospital did not detail what commands the boy responded to after he arrived. Wong later told The Associated Press she could not say if the responses were an indication that he had regained consciousness. The boy's name and hometown have not been released at the request of the family, she said.
Michigan City, Ind., Fire Chief Ronnie Martin told WSBT-TV on Saturday that an air pocket saved the boy's life.
According to Bruce Rowe, a ranger at the Indiana Dunes National Lakeshore park along Lake Michigan, the boy's family said he was playing on the dune Friday when he dropped partially into it. While they were trying to dig him out, the dune collapsed, burying the boy under 11 feet of sand, he said.
The family called 911, and emergency responders were on the scene within 15 minutes and began digging by hand, Rowe said. Crews with excavating equipment were brought in to aid the rescue effort.
Martin told the South Bend, Ind.-area TV station that firefighters located the boy while prodding the dune, right after they detected the air pocket that enabled him to survive for so long underground. They pulled him out and the boy was rushed to a Michigan City hospital, then later flown to Comer.
LaPorte County Deputy Coroner Mark Huffman told The News-Dispatch of Michigan City that the boy's survival was a "miracle."
"It is totally amazing," he said.
Authorities were puzzled about the cause of the collapse, which Rowe called "unprecedented." The section of the dune, which is more than 125 feet high and is known as Mount Baldy, had been cordoned off for restoration work. It will remain closed at least through the weekend and until authorities can determine if it's still a danger.
Wong, the Comer spokeswoman, said the boy's family wanted to express is gratitude to the emergency responders and everyone else who helped in his rescue.
"They also ask that people include this little boy in their prayers," she said.