Ill workers at an Indiana slaughterhouse where compressed air was used to remove pig brains have symptoms similar to those involved in an earlier outbreak at the Quality Pork Processing slaughterhouse, federal health officials said Wednesday.

The employees who became ill worked on the killing floors '"head tables," where the animals' heads are processed, Centers for Disease Control spokeswoman Lola Russell said. Both plants shoot compressed air into the skulls until the pigs' brains come spilling out.

"It may be associated with this particular technique of using high-pressure air to remove the pig's brain," Russell said.

The Indiana workers' symptoms included changes in sensation and weakness in their limbs, Russell said. Those symptoms are similar to a mysterious cluster of neurological symptoms reported last month among 12 workers at QPP.

The number of sick workers in Indiana, details of their conditions, the name of the company and the company's location were not disclosed.

Elizabeth Hart, a spokeswoman for the Indiana State Department of Health, said she could not comment until a meeting with a state epidemiologist set for Thursday morning.

In the QPP case, health officials suspect the workers were exposed to something in the brain tissue that triggered the illness. Officials are continuing to investigate, but so far they haven't identified any viruses or bacteria that could be causing the disease.

Five of the 12 workers afflicted have been diagnosed with chronic inflammatory demyelinating polyneuropathy, or CIDP, a rare immune disorder that attacks the nerves and produces tingling, numbness and weakness in the arms and legs, sometimes causing lasting damage.

Dr. Kenneth Gorson, a neurologist at St. Elizabeth's Medical Center in Boston, has said that victims can recover fairly quickly if the illness is caught early. However, at least one of the Minnesota workers was told she may never work again. In advanced cases, Gorson said treatment arrests the disease but doesn't reverse its effects.

Minnesota state epidemiologist Ruth Lynfield said the discovery of the Indiana illness could help her investigation.

"That may help us figure out why these workers are getting sick," she said.

After the QPP slaughterhouse illness was reported, the CDC looked into slaughtering practices in 25 large pork processing plants in 13 states, and found only two other plants -- one in Indiana, the other in Nebraska -- that used compressed air to remove pigs' brains.

Minnesota health officials said the pork plants in all three states have voluntarily stopped that practice.

Pork brains are sometimes fried and eaten in sandwiches or with gravy in some areas. But the market is small, and the American Meat Institute, which represents many pork processors, does not track sales.