Heavy winds split the popular tourist attraction in half last Friday and the remaining part is rotten, making it vulnerable to future storms, The Columbus (Ohio) Dispatch reported.
The family that owns the Richland County, Ohio, farm on which the tree is located declined to comment on its fate, the Dispatch said, adding the oak is at least 175 years old.
"I don't know how pervasive this rotting is. If it's pretty major, the next storm could knock down the rest of it, as well," Louis Andres, a regional manager for Ohio State Parks, told the newspaper.
"People really were attached to that tree," said Lee Tasseff, president of the visitors bureau for Mansfield and Richland counties. "Something in the movie struck a chord in them, and seeing the tree was almost like a pilgrimage for them."
Starring Tim Robbins and Morgan Freeman, the movie was based on a Stephen King novella. It chronicles the friendship two inmates form in a prison starting in the 1940s.