Two of the sites at the centre of the horse DNA contamination scandal have had their British Retail Consortium certification suspended pending full audits, the BRC has said.

Certification for Silvercrest Foods – owned by ABP Food Group – and Liffey Meats was removed on 18 January, after a survey by the Food Safety Authority of Ireland found horse and pig DNA in a number of beef burgers produced at both sites.

The third site involved in the scandal – ABP-owned Dalepak Hambleton in Yorkshire – was also suspended on 18 January, but has since had its BRC certification reinstated after passing an audit. New tests by Trading Standards on burgers produced at Dalepak also came back negative for horse and pig DNA today.

The BRC said certification at the sites had been suspended as a precautionary measure while investigations into the contamination problem continued. It added BRC accreditation bodies would carry out audits at Silvercrest and Liffey shortly as soon as possible.

The Irish department for agriculture, food and the marine carried out new DNA tests on burgers produced at Liffey last week, and this time around none tested positive for horse DNA. Tests at Silvercrest are still ongoing.

Earlier today, Irish agriculture minister Simon Coveney said more than 130 samples of burgers and ingredients had been taken from Silvercrest, and the results were now in the process of being verified. “As part of this process, some 24 preliminary results were received late last night (Thursday, 24 January) from a laboratory in Germany and these have been sent to an Irish laboratory for confirmatory quantitative analysis,” he added.

The department said it was unable to say when the first results would be announced.

ABP Food Group suspended all production at Silvercrest last week pending investigations. Earlier this week, Burger King announced it had dropped Silvercrest as a supplier of beef patties for its burgers.

Silvercrest and Liffey did not comment.