Nathan Woessner was taken to Comer Children's Hospital after he fell into and was buried a a sand hole at the Indiana Dunes. (Credit: Woessner Family Photo)

Nathan Woessner was taken to Comer Children’s Hospital after he fell into and was buried a a sand hole at the Indiana Dunes. (Credit: Woessner Family Photo)

UPDATE: 7/15/2013 11:55 a.m.

CHICAGO (CBS) — Relatives say a six-year-old boy is showing encouraging signs after being swallowed by a sand dune Friday in northwest Indiana.

Authorities say Nathan Woessner was underground for more than three hours.

Michigan City rescue officials say he survived because he was trapped in an air pocket.

His grandfather, First Baptist Senior Pastor Don Reul, says Nathan is responsive and is moving his arms and legs.

He remains sedated and on a ventilator as doctors at Comer Children’s Hospital continue to clear sand from his lungs. His neurological function appear to be normal.

“He was nowhere to be seen.” said Reul. “The ground had swallowed him up. Nathan was hollering out and they frantically began to dig him out. As they dug, he went deeper and deeper.”

Nathan also has 22 staples from a head injury after plunging 11 feet into the sand hole.

“God gave you a miracle,” Reul said.

He remains hospitalized in critical condition. Doctors hope to take him off the ventilator this week and believe he can be released from the hospital on 10 to 14 days.

Reul’s First Baptist Church held a prayer vigil Sunday at the church in Galva, Ill.

The boy became trapped at Mount Baldy at the Indiana Dunes in Michigan City, Ind., around 4:30 p.m. Chicago time. Park rangers say the boy’s plight quickly became worse.

“As they were trying to free him the hole completely collapsed, burying him so they could no longer see him,” Bruce Rowe of the National Park Service said.

The boy’s family made frantic 9-1-1 calls, drawing first responders within minutes, WSBT-TV reported. The heavy-equipment dig to recover him took 3 1/2 hours.

When it was over – the boy was taken away in an ambulance around 8 p.m. – some rescue workers appeared emotionally spent.

What caused this unusual accident? CBS2’s Mike Parker reports that experts theorize that perhaps a decayed tree, buried under the dune for hundreds of years, somehow created what   geologists call a “void,” or empty space, deep in the sand.

Experts will soon begin ground radar exploration to try to solve the mystery.

Meanwhile, the Mt. Baldy area is now closed indefinitely.

North of the accident, in Beverly Shores, beachgoers are out in force, including fans of the now shuttered Mt. Baldy.

Teresa Carnahan of Portage told CBS 2, “The kids love it.  I’ve always loved climbing up that big hill.”

Now, she says, “The lake is dangerous enough. Now you’ve got to worry about this.”

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