A 63-year-old man was also arrested at Peter Boddy Slaughterhouse in West Yorkshire, the other plant where operations were suspended on Tuesday in an investigation by the Food Standards Agency.
Dyfed-Powys Police has confirmed three people are being held on suspicion of offences under the Fraud Act.
They are being detained at Aberystwyth Police Station, where they will be interviewed jointly by the police and the FSA.
More top news
Traders across Wales have told ITV News the migrant crisis in Calais is having a 'devastating' impact on their business.
The Balmoral is back but for how long? Volunteers appeal for public support to keep her sailing the Bristol Channel.
An 'offensive and indecent' novel entered into a National Eisteddfod writing competition is being investigated by police.