AUSTIN, Minn. (AP) ― Another meatpacker appears to have developed the neurological symptoms identified in 12 other workers that sparked a nationwide investigation.

Unlike the others, however, the worker was not stationed near the high-powered air compressor system used to remove pig brain tissue at Quality Pork Processors. Rather, the worker was exposed to brain tissue in the rendering operation in the basement of the plant QPP shares with Hormel Foods.

State epidemiologist Ruth Lynfield said, "We are investigating a likely additional case."

QPP employs 1,300 workers and slaughters pigs on one side of the plant. On the other side, an estimated 1,400 Hormel workers process the meat into bacon and other products. Hormel owns the rendering operation.

The first 12 cases of the disease involved employees working at the "head table" of QPP, which was spun off from Hormel in 1989. QPP halted the process of blowing out brains with the air compression system as soon as the December investigation began.

As a result of the most recent suspected case, health officials are expanding the investigation to include Hormel workers in and around the rendering operation, according to a notice to employees posted in the plant Tuesday.

The meatpackers in Austin and two at a plant in Indiana have reported fatigue, numbness and tingling in their arms and legs, with a wide range in severity. A few are severely disabled, while others have been treated and returned to work.

State and federal health officials are looking into whether pig brain tissue, liquefied during removal by the air-compression system and sprayed into the air as droplets, somehow caused nerve damage in workers who were exposed to it.

Investigators theorize that a protein or other substance from the animal brains triggered the workers' immune systems into mistakenly attacking their own nerve tissue.

The brains are frozen in boxes and shipped to the southern United States and Asia, where they are sold as food.

Last week, state officials said they were broadening the investigation of the QPP section of the plant to thousands of former meat packers going back a decade, to when the powerful air-compression system was first installed.