PHILADELPHIA – Wampler Foods recalled all cooked deli products made since May at a suburban plant and halted production because the meat is possibly contaminated with listeria, authorities said Sunday.

The recall of about 27.4 million pounds of meat is the largest in USDA history. It follows an Oct. 9 recall of 295,000 pounds of turkey and chicken products at the plant in Franconia.

The company voluntarily expanded the recall to all cooked deli products made from May 1 through Oct. 11 and halted production Saturday at the facility about 25 miles north of Philadelphia after receiving test results of samples taken from floor drains.