Three men - including the owner of a meat processing plant - have been arrested in relation to the horsemeat scandal.
Farmbox Meats owner Dafydd Raw-Rees, 64, and a 42-year-old man were arrested at the firm's plant in Aberystwyth on suspicion of offences under the Fraud Act.
A 63-year-old man was also arrested on suspicion of the same offence at Peter Boddy Slaughterhouse in Todmorden, West Yorkshire. Both sites were inspected on Tuesday by the Food Standards Agency (FSA).
A Dyfed-Powys Police spokesman said: "Approvals for both operations were suspended yesterday by the FSA so neither firm was operational.
"Dyfed Powys Police can confirm the three people have been arrested on suspicion of offences under the Fraud Act and they are being detained at Aberystwyth Police Station where they will be interviewed jointly by police and FSA staff in what has this afternoon become a joint operation."
The two plants became the first UK suppliers suspected of passing off horsemeat for beef.
Production at both plants was suspended pending the outcome of investigations into claims they supplied and used horse carcasses in meat products purporting to be beef for burgers and kebabs.
The FSA previously said it had "detained" all meat found at the premises and seized paperwork and customer lists from the two companies.
It comes after it emerged low levels of a potentially dangerous drug were found in horsemeat destined for human consumption.
Figures released by the FSA showed eight horses slaughtered in the UK between January 30 and February 7 tested positive for the veterinary painkiller bute.
But no evidence of the drug was found during FSA tests on Findus processed beef products withdrawn from sale in the UK after the discovery of traces of horsemeat.
Chief Medical Officer Dame Sally Davies said the contaminated horsemeat contained much lower levels of bute than those used to treat patients.
"If you ate 100% horse burgers of 250g, you would have to eat, in one day, more than 500 or 600 to get to a human dose," she said.
"It would really be difficult to get up to a human dose."
Meanwhile, Asda announced it was withdrawing its 500g Beef Bolognese sauce from stores after preliminary test results suggested the presence of horse DNA.
The company apologised to customers and said it was taking a "belt-and-braces approach" by removing a further three beef products made by the same supplier, the Greencore plant in Bristol, as a precaution.
Sainsbury's and the Co-op confirmed they were also supplied by Greencore.
Sainsbury's said it was carrying out tests for the presence of horse DNA but added that Greencore used a different beef supplier for its products.