Reports in Taiwan alleged that bread sold by the sandwich chain Subway contained an ingredient not permitted under local rules, and that some sauces used unsuitable oil.

After the reports, the company said the products in question had already been taken off shelves, with the scope and volume of the recall and the findings of its inquiry to be disclosed later.

Food additive standards differ by country. Ingredients allowed in one jurisdiction are often banned or capped at lower levels in another, which is how multinational chains end up out of step with local rules.

The question about oil concerns processing. Fats reused at high temperatures or insufficiently refined can generate harmful compounds, which makes records of raw-material handling a focus of inspection.

Taiwan's health authorities typically examine imported inputs and local processing together. Confirmed violations bring fines and orders to destroy the product.

Consumers can verify little on their own. Beyond ingredient lists and expiry dates on packaging, the origin of inputs is hard to trace, which makes publication of inspection results important.

A franchise runs on both headquarters standards and a local supply chain. Depending on where inputs are sourced, the same brand can have different formulations from country to country.