Suspicions of criminal involvement in Europe’s continent-wide food-fraud scandal deepened yesterday — even as the origin of horsemeat sold as frozen beef remained a mystery.

Spanghero, the French meat-processing firm at the scandal’s center, revealed a plan to sue a Romanian supplier that allegedly mislabeled the horsemeat, which has found its way to shelves in at least three countries.

But Spanghero officials declined to name the supplier or to explain why they allegedly resold the meat as 100 percent French beef.