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.
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Wales could be without star number eight Taulupe Faletau for this season's Six Nations.
Icy in places as we start the day with strong winds and heavy rain pushing in. This will clear and this afternoon looks much brighter!
A milder feel than last night but there's wind and rain on the way, and ice will form in places too!