The area around Mount Baldy, at the Indiana Dunes National Lakeshore, will remain closed indefinitely after officials reported finding a second sinkhole near the area where a 6-year-old boy was swallowed up last month.
Crews from the Environmental Protection Agency this week found the hole, which is about 10 inches in diameter and at least five feet deep, during a sweep of the area with ground-penetrating radar.
"This is obviously a very rare occurrence but we know it's not a unique occurrence," said park ranger Bruce Rowe.
He said officials noticed the sand at the bottom of the sinkhole was loose, leading them to believe the hole may have been much deeper and had slowly been filling in with sand.
One theory is that a decomposed tree trunk under the dune created the void that swallowed Nathan Woessner on July 12. The theory is based on some old rotted wood or wood fiber found in the area where the boy was rescued, Rowe said.
Emergency workers freed Woessner after he was trapped under 11 feet of sand for more than three hours. He was unresponsive when initially rescued, but began breathing en route to a waiting ambulance. He's since undergone some physical, occupational and speech therapy and is expected to undergo more rehabilitation.