First responders from Carmel arrived to find a 34-year-old worker trapped, the television station reported.
Officials with the Indianapolis Fire Department believe the man was measuring the silo's interior when he stepped onto an air pocket in the gravel, which sucked him down into a hole, WXIN reported.
The man fell approximately 30 feet into the silo. Seven rescuers descended into the silo and moved the man into space measuring 18 feet by 18 feet, the television station reported.
"What you're dealing with inside the gravel was basically trying to remove pieces of concrete, it's just that heavy. It's not workable. Every time they tried to move the concrete there was no place for it to go," Indianapolis Fire Department spokeswoman Rita Reith told WXIN.
Using a giant shop vacuum, crews were eventually able to remove the gravel so it only went as high as the man’s waist, the television station reported. Then, they released some gravel from a door at the bottom of the silo and pulled the man to safety.
"This is something that not only the victim was already in danger, but putting rescuers down in there, if anything would have gone wrong, you know the gravel just as it had sucked him in it would have sucked in the rescuers as well," Reith told WXIN. "It's all about timing and finessing the situation."
The man is in fair condition with no visible injuries, the Indiana Fire Department said.