Retailers and their processed meat suppliers are bracing themselves for a potential new wave of damaging horse DNA revelations, as laboratories in the UK and abroad are being inundated with requests to test products for traces of equine.

Genon Laboratories in the UK has been asked to run about 400 horse DNA tests since the contamination scandal broke last week, and general manager Angela Bromley said some samples had come back positive for horse.

“It’s been absolutely crazy - we’ve had samples sent in from pretty much every lab in the country, and we’ve even had to bring in staff at the weekend, which isn’t something we normally do,” she said.

Genon declined to say how many samples had tested positive or which clients or products were involved. However, Bromley revealed Genon had also received requests for testing from TV crews and other media companies.

Genetic ID in Germany - which carries out DNA tests for clients across Europe - said it had also had numerous enquiries from the UK and Ireland as a result of the scandal, including one from an Irish newspaper. It declined to say whether it had agreed to run tests for the paper.

CEO Bill Thompson said Genetic ID was just about to start running horse DNA tests for its clients and was expecting results later this week.He added clients were typically asking for either two or three species to be tested - beef and horse, or beef, horse and pig.

The revelation that horse DNA has already been found in some samples - coupled with the fact that some of the tests were commissioned by the media - is a worrisome prospect for meat suppliers and their customers, as it raises the prospect the contamination problem could be widened to products and retailers that had not so far been implicated in the scandal.

Tests by Irish regulators carried out last year and announced earlier this month found horse DNA in burgers produced by Silvercrest Foods and Dalepak Hambleton (both owned by ABP) as well as Liffey Meats.