Feds Launch Probe Into 'Mt. Baldy' Dune Collapse

UPDATED: 8/12/2013 1:55 p.m.

MICHIGAN CITY, Ind. (CBS) -- The National Park Service and U.S. Environmental Protection Agency will be examining the Northwest Indiana sand dune that collapsed last month, burying a 6-year-old boy under 11 feet of sand for more than three hours.

Federal investigators used "ground-sensing equipment" on Monday to investigate Mount Baldy - a 43-acre sand dune at the Indiana Dunes National Lakeshore near Michigan City, Ind.

The radar will be able to look under the dunes for other holes or hazards beneath the sand.

"It is a project beyond the scope of what we've done before," said Bruce Rowe of the National Park Service. "It's certainly unknown, which makes it difficult, but it's one step at a time."

And it is one sandy step at a time.

The lawn mower-looking instrument takes pictures of the earth from above, while a backpack using high-powered GPS measures coordinates. That way, scientists know exactly where to go if they have to dig.

"This equipment is normally used for criminal investigations, if we're looking for buried hazardous waste, abandoned pipe lines, that kind of thing," said Environmental Protection Agency spokesman Francisco Arcuate.

Crews spent hours pushing and waking through the dunes to see if there is a chance the ground could open up again.

That section of the park has been closed to the public since July 12 when Nathan Woessner of Sterling, Ill., disappeared into the collapsed sand.

He was in the hospital for two weeks before returning home.

Rescue officials say he survived because he was trapped in an air pocket.

He was treated at the University of Chicago's Comer Children's hospital, for critical injuries to his lungs after inhaling sand.

He was released last month, after a recovery that amazed his father, Greg Woessner.

"To be where we are, after only two weeks, is phenomenal," Greg Woessner said.