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
Supermarket worker denied raping a 24-year-old, claiming he was at home with his wife.
Officers from South Wales Police are among those searching for 16-year-old Becky Watts from Bristol, who disappeared eight days ago.
As Wales prepares to face France at Stade de France tomorrow, here are 10 match facts about the two sides.