Public outrage is mounting in China over allegations that a major state-owned food company has been cutting costs by using the same tankers to carry fuel and cooking oil – without cleaning them in between.

The scandal, which implicates China’s largest grain storage and transport company Sinograin, and private conglomerate Hopefull Grain and Oil Group, has raised concerns of food contamination in a country rocked in recent decades by a string of food and drug safety scares – and evoked harsh criticism from Chinese state media.

It was an “open secret” in the transport industry that the tankers were doing double duty, according to a report in the state-linked outlet Beijing News last week, which alleged that trucks carrying certain fuel or chemical liquids were also used to transport edible liquids such as cooking oil, syrup and soybean oil, without proper cleaning procedures.