Tesco has withdrawn a frozen meatloaf after tests showed it contained horsemeat.

The frozen 600g Tesco Simply Roast Meatloaf tested positive for between 2% and 5% horsemeat. It was manufactured between October 2012 and January 2013 by Eurostock Food Group, Northern Ireland.

“Our investigation to thoroughly understand the source of the contamination has started and we will complete our investigation before deciding whether to continue using the supplier,” said Tim Smith, Tesco group technical director.

Tests on 15 other lines from the same manufacturing site did not identify horsemeat. In total, Tesco has tested over 500 products identified as being most at risk of containing horsemeat. The meatloaf is the fourth Tesco-branded product to have tested positive. 

“We are very sorry that we have had a further product which has failed to meet the high standards we and our customers expect,” Smith added.

Eurostock said it was “shocked and disappointed” by the test result. “The integrity of our supply chain is vital and we are working closely with our customers to try to establish the source of the contaminating material,” it said in a statement, adding that investigations were on going and it remained in constant dialogue with all relevant parties. It did not name which other customers were affected by the news.