China is freaking out over an 'open secret' that its cooking oil was ferried for years in chemical tanks that weren't cleaned

• China has been hit by another major food scandal, this time involving cooking oil in chemical tanks.
• State media found tank trucks were delivering chemicals and edible oil interchangeably without cleaning.

A new cooking-oil scandal has erupted in China, about a decade after the country's infamous crackdown on restaurants reusing gutter oil and sewage grease.

The furor follows a bombshell investigation published on July 2 by the state media outlet Beijing News, which found multiple cases of tank trucks transporting edible cooking oil immediately after delivering chemicals used for coal-to-liquid processing.

The report's author, Han Futao, found that none of the tank interiors were cleaned between loads.

Han described one case in which a tank truck in Hebei province delivered chemicals in Qinhuangdao before rushing to Sanhe days later to be filled with soy oil.

Several truck drivers told Beijing News the practice was a widespread cost-saving measure used by firms with thousands of trucks — an "open secret" in the industry, Han wrote.

In some seasons, the truckers said, drivers would transport industrial wastewater before delivering edible oils.

These chemicals aren't classified as flammable or hazardous, or else Chinese law would mandate that they be transported in special tanks.

The report has since ignited outrage on China's social-media platforms, which have become inundated with viral topics discussing the scandal.

National regulations have been a key target for public anger. They recommend that oil companies use tank trucks dedicated to edible substances, but the guideline is only encouraged and isn't mandatory.

"Shouldn't a kerosene can be a kerosene can and a cooking-oil can be a cooking-oil can? Even if they are cleaned, they are not necessarily that clean," one top comment on Weibo, China's version of X, said.

The backlash ballooned even further when people began reposting regulatory warnings from 2013 about the practice in Hunan province, indicating its use for more than a decade.

A 2005 local news report describing the mixing of edible oils with "hazardous chemicals" during transport went viral, too.

"They've been caught before, but the problem persists. Is the punishment harsh enough?" one blogger wrote.

"19 years ago, the media reported that the tanks were mixed with food. Why hasn't it been solved yet?" another wrote.

Days after Beijing News' report, state media jumped in with scathing commentary.

"If this is an 'open secret in the industry,' where does it put the public's health and life safety? Where does it put the dignity and justice of the law?" the People's Daily columnist Zhang Jingshan wrote on Monday evening.

Sinograin, a state body that oversees China's grain and oil stocks, published a statement on Saturday saying it had launched an investigation into the "mixed use of tank trucks."

But the statement has been followed by calls online for a wider investigation involving higher authorities.

"Checking your own unit is like covering your ears while stealing a bell," wrote one blogger demanding an explanation. "This needs the attention of the relevant departments. Food is a major issue of people's livelihoods and shouldn't be underestimated!"

Food safety in China has already been a sensitive topic for years in the wake of multiple scandals involving gutter oil and deadly chemicals in baby milk powder.

The repeated controversies have contributed to growing distrust in cities toward commercially sold foods in supermarkets and grocery stores, sparking a campaign by the central government to promote food safety in the country.