The origin of the recent salmonella outbreak remains unclear as the number of cases in Pennsylvania alone hit seventy, and a Seattle-based law firm announced it will file suit Monday on behalf of at least one area couple.

Bill Marler of the Seattle law firm Marler Clark – which specializes in cases involving food-borne illness – said he will file the suit Monday on behalf of six people sickened in the outbreak, including a couple from Butler according to Amanda Gillooly of the Times.

Marler indicated Sheetz is legally liable for tainted food sold at its convenience stores but said he is more inclined to sue the supplier who provided the food.

About 44 samples of lettuce, tomatoes, cheese and mayonnaise taken from 10 Sheetz convenience stores across the state showed no trace of the salmonella bacteria, a state Department of Agriculture spokesman said. Testing of an additional 197 food samples will resume over the weekend.