How can I check claims that beef was mislabeled as horse meat?

First separate a specific, documented incident from a rumor about where meat comes from. A shipment being rejected, or a country being named as the source, doesn’t by itself show that beef was switched for horse meat. Look for a food-safety notice that identifies products or batches and explains what was tested and found.

I’d look for traceable details: the product name, batch or lot information, dates, and a clear account of how the species was identified. Without those, it’s hard to tell whether a post is describing a verified finding, repeating an allegation, or mixing it up with a separate import issue.

If the concern is about something currently for sale, check relevant food-safety agency notices and contact the retailer or manufacturer with the label details. Don’t treat a country of origin as proof of mislabeling.

There are two questions that often get tangled together: whether a shipment meets import or safety rules, and whether the meat was accurately labeled as a particular species. Evidence for one doesn’t automatically answer the other. I’d wait for a documented test or an official investigation before sharing a specific accusation as fact.