US supermarket group Kroger has withdrawn packs of its own-label Mustard and Southern-Style potato salad after fears that they may be contaminated with E. coli O157:H7.

The packs concerned bear a "best if used by" date of 5 September. Customers have been encouraged to return any such products to a store for a full refund.

The Ohio Department of Agriculture (ODA) tested a sample of the product collected during routine food safety sampling and found it contained the foodborne pathogen. However, Kroger said that third parties that had analysed several other samples from this code date had found no strains of E. coli O157:H7. The retailer also said that to date no illnesses had been reported.

"This voluntary product withdrawal was undertaken as a precuationary measure," the company said in a statement.

Kroger stressed that the recall does not extend to its Fred Meyer, QFC or Ralphs chains because the product was not distributed in these divisions.