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
A family has issued an appeal to help find their missing pet turkey - in case he gets gobbled up as someone's Christmas dinner.
A blustery start to the weekend with sunny spells and scattered showers.
Welsh Secretary Stephen Crabb has launched an attack on Labour leader Ed Miliband, saying he "doesn't give a toss about Wales".