Recalls of potentially contaminated meat may not be as effective in removing products from the market as the US Department of Agriculture has reported, according to an agency audit.

The report said the USDA’s Food Safety and Inspection Service’s “conclusions regarding the effectiveness of food safety recalls may be based on inaccurate or incomplete information”, reported the Associated Press.

The USDA inspector general’s office looked into one of the largest recalls of the last few years, when 27.4 million pounds of processed deli poultry meat was recalled due to possible listeria contamination. The recall was initiated by US meat processor Pilgrim’s Pride, which owned the Franconia, Pa. plant where the meat had been processed, and monitored by the FSIS.

The recall recovered more than 5.5 million pounds of meat before it was ended several months later when the FSIS determined it had been effective. However, the inspector general’s office said there were holes in the records on which the FSIS had based its determination; discrepancies were found in 389 of the 582 effectiveness check forms that the office examined.

“We attributed this high error rate to the careless approach FSIS compliance officers and supervisory personnel took in overseeing the recall,” the Associated Press quoted the report as saying.

The FSIS said it has made several changes to its methods for tracking recalls’ effectiveness since the Franconia recall. The agency said it has strengthened verification activities and established clearer lines of authority.