Tanker trucks in China transporting edible oils and chemicals without proper cleanings in between trips cross the bottom line of food safety management and reflect a lack of quality control among involved enterprises, said an industry expert.

Edible oil makers should strengthen their quality control efforts, trace the flow of products transported by tanker trucks, actively recall related products and compensate consumers accordingly, said Zhu Danpeng, an independent food and beverage industry analyst, following reports of tankers having illegal mixtures of cargo.

Edible oils should be transported in special containers and not in tankers used for nonedible products, according to Chinese regulations. The issue has sparked outrage among the public and led to a plunge in share prices of edible oil companies.

China Grain Reserves Group Ltd Co (Sinograin), the country's largest grain storage and transport company, was reportedly involved in mixed and contaminated cargo transport cases and has since removed edible oil products from Jinding, a brand affiliated with the group, from its online flagship stores on Taobao and JD.

Shenzhen-listed Jinlongyu, a major domestic producer of packed edible oils affiliated with Yihai Kerry Arawana Holdings Co Ltd — a major domestic agricultural and food products processor — reported mixed transport of edible oils at its plants in Wuhan, Hubei province, and Shaanxi province.

Shares of Jinlongyu fell 4.41 percent to close at 26.04 yuan ($3.58) on Wednesday amid food safety concerns.

"It is common knowledge and practice for enterprises to clean the holding tanks of trucks when replacing transported cargo. The mixed transport of coal-based liquids and edible oils has exceeded people's imaginations and crosses the bottom line of food safety," Zhu said.

He added that coal-based liquids contain chemicals that are hazardous to human health, with the possible deleterious impacts awaiting specific test results.

Jinlongyu responded that the itinerary that involved its Wuhan factory was the first transport after the tanker truck was registered, meaning the truck was brand new at the time of transport in question.

For the itinerary involving its Shaanxi plant, the tanker was cleaned and an inspection was carried out, and the results of the product quality inspection met national requirements, the company said.

In addition, Shandong province-based Luhua Group, a major domestic peanut oil producer, said it has implemented strict supervision over the transport of its cooking oil products.

The office of the food safety commission under China's State Council said on Tuesday that it has organized authorities — including the National Development and Reform Commission and the State Administration for Market Regulation — to set up a joint investigation team to look into improper use of tanker trucks in edible oil transport.