The collapse happened just before 4 p.m. at the farm on McNaught Rd. South.
A worker in his 50s was missing after the collapse and officials are now presuming he was buried under what could be as much as 50 tons of corn, said Chief Bob Vellias with South Pierce Fire and Rescue. Rescue crews stood by to search for the victim but structural engineers have been unable to guarantee the area was safe enough to enter.
Crews are expected to attempt to recover the body on Tuesday.
There is no word yet what caused the silo to collapse.