OMAHA, Neb. — ConAgra Foods Inc. voluntarily stopped production yesterday at the Missouri plant that makes its Banquet pot pies after health officials said the pies may be linked to 139 cases of salmonella in 30 states.

ConAgra officials said they believe the company's pies are safe if they're cooked properly, but the Omaha-based company told consumers yesterday not to eat its chicken or turkey pot pies until the government and company investigations are complete.

The U.S. Department of Agriculture also issued a health alert yesterday afternoon warning consumers about the suspected link between the company's product and the salmonella cases.

The federal Centers for Disease Control and Prevention has been tracking reports of the salmonella cases since last Wednesday. A CDC spokeswoman said the largest numbers of salmonella cases have been reported in Wisconsin, Pennsylvania and Missouri. There have been no cases reported in Hawai'i.

Salmonella sickens about 40,000 people a year in the U.S. and kills about 600. Most of the deaths are among people with weaker immune systems such as the elderly or very young. Salmonella can cause diarrhea, fever, dehydration, abdominal pain and vomiting. Most cases of salmonella poisoning are caused by undercooked eggs and chicken.

So far no deaths have been linked to the pot pies.

Earlier this year, ConAgra had to recall all of its peanut butter because it was linked to a different salmonella outbreak.

The USDA said the Marshall, Mo., plant makes Banquet and generic store brand pot pies. All of the pot pies made at the plant in question have "P-9" printed on the side of the box as part of a code above the use-by date.

ConAgra spokeswoman Steph-anie Childs said she didn't know how many people work at the Marshall plant or how the shutdown will affect them.

Federal officials said consumers shouldn't throw away or eat the chicken or turkey pot pies until the Food Safety and Inspection Service can determine the source of the salmonella contamination and verify proper cooking instructions.

ConAgra is offering refunds to consumers, but no recall of pot pies was being planned yesterday.

Childs said ConAgra is confident in the safety of its chicken and turkey pot pies when all the cooking instructions on the package are followed. It is especially important to follow the directions when the pies are cooked in a microwave.

Pot pies need to be cooked longer in microwaves that have less power, Childs said. A good sign that the pot pie is done is when steam rises out of it.

Childs said the cooking will kill any common pathogens routinely found in uncooked products that contain poultry.

The company already is planning to revise the cooking directions on its packages to clarify how long the pot pies should be cooked in different microwaves.

Currently, the Banquet pot pie package advises consumers to cook the product for 4 minutes in a medium- or high-wattage microwave or for 6 minutes in a low-wattage microwave. But the package doesn't define a low-, medium- or high-wattage microwave.

Childs said ConAgra is working with federal investigators to determine whether additional precautions are necessary.

"If any indications are found that the product poses risks to consumers when cooked according to package directions, the company will take further action immediately," ConAgra said.

Michigan State University professor Elliot Ryser, a food microbiologist, said consumers shouldn't have to worry much about pot pies in general as long as they are completely cooked.

But microwaves may heat food unevenly, said Ryser, who is part of the university's National Food Safety & Toxicology Center.

"If you're going to heat that product uniformly, it requires some diligence on the part of the consumer," Ryser said.

In February, the CDC linked ConAgra's peanut butter, including Peter Pan, to the illnesses of more than 625 people in 47 states.

ConAgra resumed shipping Peter Pan in August. The company faces several lawsuits by people who said they became ill after eating Peter Pan.