The silo collapsed Monday afternoon at Wilcox Farms and in the process, caused an adjacent silo to lose its support system and lean against the first damaged structure, South Pierce Fire & Rescue Chief Bob Vellias said.
One of the silos was empty, but the other was filled with 50 tons of corn, which spilled out into another nearby building, filling an office and electrical area with corn, Vellias said.
Four workers were in the office at the time of the incident, and three were able to escape, The (Tacoma) News Tribune reported.
A man was missing after the accident, but rescuers were unable to remove the spilled corn to search for him because it was the only thing keeping the damaged structures from collapsing further, the newspaper said.
"We're really unable to remove any of the grain, because it would jeopardize the structure," Vellias said.
"We're still holding out for the best, but we won't know until later. It's probably a pretty long operation we're looking at here."
An engineer with the Federal Emergency Management Agency arrived at the egg farm to assess the structure to determine if it was safe for a rescue operation, The News Tribune said.