Taiwan's prosecutors have charged four food companies and 15 executives over cooking oil laced with a cancer-causing chemical, a serious blow to the firms and to consumer trust in the island's food industry.

• Central Union Oil Corp made seven batches of soybean oil with too much benzopyrene, a known carcinogen, and it reached more than 13,000 businesses across Taiwan.
• Executives knew imported soybeans from Brazil were heat-damaged and raised the allowed damage limit tenfold without adding extra testing.
• Bad test results showed up in May, but the company did not warn regulators or pull the oil, and later underreported how much tainted oil was sitting in one storage tank.
• Taisun, Fwusow and Formosa Oilseed took the contaminated oil, repackaged and kept selling it to food makers and shoppers who had no idea.
• Prosecutors put the illegal profits at roughly NT$887 million and want that money clawed back, along with the companies' property; four executives are being held in detention.

Outlook: The four companies face criminal trials, asset seizures and lasting damage to their brands, and Taiwan's food regulators are likely to tighten oversight of oil producers.