A couple sued ConAgra Foods Inc. on Friday over a salmonella outbreak linked to its peanut butter, and their attorney said more suits will follow.

The lawsuit was filed in U.S. District Court in Kansas City by Susanna and Brian Cox of St. Joseph. It claims that Susanna Cox and the couple's two children began developing gastrointestinal illnesses in October after eating Great Value Peanut Butter, made by ConAgra. The two children required urgent medical treatment, according to the lawsuit.

The couple seek unspecified damages.

Seattle-based attorney William Marler, whose firm handles many cases of food-borne illness, said the lawsuit is the first in the outbreak, which has sickened nearly 300 people in 39 states since August. No deaths have been reported.

Click here for more details on the peanut-butter brands affected.

The possible link to tainted peanut butter became known Wednesday when Omaha, Neb.-based ConAgra and the Food and Drug Administration announced a product recall.

Federal health investigators have said they strongly suspect Peter Pan peanut butter and certain batches of Wal-Mart's Great Value house brand, both manufactured by ConAgra.

ConAgra spokesman Chris Kircher declined to comment on specifics of the lawsuit, but added, "We take any consumer concern over the recall very seriously, because consumer safety is our top priority."

Marler said Friday that 450 people had contacted his law firm this week.

Salmonella sickens about 40,000 people a year in the U.S. and kills about 600. It can cause diarrhea, fever, dehydration, abdominal pain and vomiting. The only known salmonella outbreak in peanut butter — in Australia during the mid-1990s — was blamed on unsanitary plant conditions.