Two chains of food stores have invited consumers to return tins of sliced beef they may still have at home after they became caught by the horsemeat contamination scandal.

Home Bargains and Quality Save have withdrawn supplies of canned sliced beef from a batch made in Romania in January, the Food Standards Agency said on Thursday.

TJ Morris, their parent company, said it was told about the presence of equine DNA on 30 September and had immediately taken the beef off the shelves. The product was made by Scandia Food in Romania.

Routine tests by Lincolnshire county council on the food hall sliced beef in rich gravy, discovered 1%-5% of horse DNA, although the meat tested negative for phenylbutazone, the equine inflammatory drug banned in food. The announcement of the finding however was delayed because TJ Morris exercised its right to test the same sample.

The affected batch has a best beforedate of January 2016 and a batch code of 13.04.C.

TJ Morris said it was disappointed with the findings, saying that the factory had "the highest level of UK food standards accreditation".

It called the amount of horse DNA "diminutive" and said it was found in a batch made before horsemeat was found in other products. Other batches of the sliced beef had since been tested and they had no trace of horsemeat.

"We work closely with our suppliers to ensure that our quality control is of the highest standard and extremely thorough," said the TJ Morris statement. "We are already liaising with this supplier to ensure that an even more robust process is in place moving forward."

Eighteen companies had between them 29 products containing more than 1% horsemeat, since the scandal broke in January. Only a corned beef line sold by Asda has tested positive for bute.

There is increasing unease at the apparent lack of information from authorities in the UK, Ireland and elsewhere on how the scandal came about.

The FSA said that so far results of 36,395 beef samples tested for horse DNA had been submitted to it by the food industry. Of these, 47 samples, from 29 products, were positive.

Local authorities had taken 2,390 samples either for their own testing or as part of a survey for the agency.