School of Forest Resource Director Mike Messina told WJAC-TV Friday that a phenomenon underground is causing the first floor to rise as much as one inch in some classrooms.

"That gravel has undergone a chemical reaction, causing it to swell,” said Messina. “Since it can't swell down, it has swollen up. It's lifting the floor. The building isn't sinking; the floor is rising a little bit, causing some cracks in the wall and maybe getting some doors stuck."

Despite rumors, noticable cracks in the drywall and shifting of floor tiles, Penn State officials said the building is structurally sound.

“Apparently the gravel came from a local quarry that was not known to have any kind of pyrite in the gravel, so this was a complete surprise,” said Messina. “We were kind of blindsided."

University officials say they will have to remove the gravel underneath the building and replace it, a project that will keep the building closed for several months starting in January.

A projected cost for the fix hasn’t been released; university officials said they expect the contractors to pay for the repair project.