The agency says "dead rodents, rodent excrement and bird feathers" were discovered Wednesday in a crawl space above a production area.
The state inspection also found that the unit's air handling system was pulling debris from the infested crawl space into production areas.
The plant began operating in March 2005, but was shut down by the company earlier this week.
The health department order Thursday also requires the plant, which began operations in March 2005, to stop producing and distributing food products.
Plainview is in the Texas Panhandle.
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