The Chinese government says it will investigate allegations that fuel tankers have been used to transport cooking oil after carrying toxic chemicals without being cleaned properly between loads.

The controversy has spread online as social media users express concerns about potential food contamination.

Tankers used for transporting fuel were found to be carrying food products, like cooking oil and syrup, and were not decontaminated correctly, according to state-run Beijing News.

Transporting cooking oil in contaminated fuel trucks was said to have been so widespread it was considered an “open secret” in the industry, according to one driver quoted by the newspaper.

The case is the latest blow to public trust in the Chinese government's ability to enforce food safety standards.

The controversy has been the top trending topic on Chinese social media in recent days.

On Weibo - the country’s equivalent to X, formerly known as Twitter - there have been tens of thousands of posts about the scandal, which have racked up millions of views.

“Food safety is the most important issue,” a comment liked more than 8,000 times said.

Another comment said: “As an ordinary person, surviving in this world itself is an amazing thing already.”

Many compared it to the 2008 Sanlu milk scandal, in which some 300,000 children became sick and at least six died after drinking powdered milk contaminated with high levels of the industrial chemical melamine.

“This is much worse than the Sanlu scandal, it can’t be settled with just [a] statement,” a user commented.

In China, tankers are not limited to any particular type of goods so can, in theory, carry food products straight after transporting coal-based oils.

The claims involve several major Chinese companies including a subsidiary of state-owned Sinograin and the Hopefull Grain and Oil Group.

Sinograin has said it is investigating whether food safety regulations were being followed correctly.

The company also said it will immediately suspend the use of any trucks that are found to have fallen foul of the the rules.

A Hopefull Grain representative told government-controlled newspaper Global Times that it was conducting a "thorough self-inspection".

The Chinese government has said food safety officials will carry out the investigation into the allegations.

They have promised to punish any companies and individuals involved in wrongdoing.

They have also vowed to immediately publish the findings of their investigation.

"Illegal enterprises and relevant responsible persons will be severely punished in accordance with the law and will not be tolerated," state broadcaster CCTV said.

At the local level, both the Hebei and Tianjin provincial governments have said they are also looking into the matter.

Additional reporting by Fan Wang