The Chinese government has launched an investigation into allegations that fuel tankers have been used to transport cooking oil without proper cleaning, sparking concerns about food contamination.

According to state-run Beijing News, tankers used for transporting fuel were found to be carrying food products, including cooking oil and syrup, without being properly decontaminated between loads.

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.

China’s State Council said Tuesday it was forming an investigation group with officials from the Food Safety Commission, the Public Safety Bureau and other ministries. “Enterprises in violation and relevant responsible persons will be severely punished according to law,” the announcement said, according to state broadcaster CCTV.

The Beijing News investigation followed one tanker from the northwestern Ningxia region, which carried a type of hydrocarbon that is converted into liquid fuel. From Ningxia, the tanker travelled to northern Tianjin and then filled up with soybean oil from Sinograin, without stopping to get clean.

The hydrocarbon products contain components that may lead to poisoning, said one expert quoted in the Beijing News story.

China Grain Reserves Group, Sinograin’s formal name, said in a statement Saturday that it was conducting an audit after the media allegations.

The investigation also followed other trucks that emerged carrying hydrocarbons from a plant belonging to the China Energy Investment Corporation, which then went on to get edible oils from other companies after they unloaded their first cargo.

The story, published last Tuesday, has since received widespread national attention as major state-owned corporations were implicated.

In 2008, many families switched to buying imported infant formula after it was found that a brand called Sanlu contained melamine in its formula, a chemical that caused kidney damage and other harm. The tainted formula killed six babies.

(With AP Inputs)