Traders are believed to have filled nearly 1,000 live chickens with mineral powder to increase their weights in Chongqing, adding new spice to the country's list of food scandals.

The chickens were found in Southwest China's Chongqing municipality during a raid jointly conducted by the local administration for industry and commerce, the public security bureau and the local highway law enforcement authority. They were being transported from Guizhou province on early Sunday morning, according to an official source.

According to Tang Chuan, an official with the municipal administration for industry and commerce, local consumers told authorities that unknown substances had been found in the digestive tracts of live chickens bought from local markets and that they feared their health might be in danger.

Since 18 April, the administration has investigated several poultry markets, collecting samples for testing.

The samples taken from the chicken's intestines were found to contain a considerable amount of barium sulphate, commonly known as barite powder.

And there were 110mg of magnesium and 1.1mg of barium for each kilogram of the chickens that were tested.

On Saturday (6 April), law enforcement officers stopped two trucks carrying suspected chickens at the toll stations of the Chongqing-Guizhou highway. The officers noticed that the chickens' crops were abnormally plump and asked the drivers to hand over several of the chickens for testing, the report said.

The tests revealed grey powder in the birds' crops.

The owners of the livestock confessed to the inspectors that each of the birds had been fed from 300 to 400 grams of barite powder. The chickens had been purchased from Zunyi, a city in Guizhou province.

The chickens were seized, and the case is under further investigation.

Barite powder is mostly used to add weight to oil drilling mud, to deflect X-rays in medical science, as a material in the brakes of vehicles and in high-quality paints.

Regular reports of incidents involving food safety have caused much concern for the Chinese. While China is working on its largest crackdown on food safety hazards, the country's food safety authority is also making efforts to better inform the public about food safety.

Before working in the food industry, a person must be trained for a such job, said the executive office of the food safety commission under the State Council, China's Cabinet, in a five-year plan (2011-2015) guiding the country's work to teach the public about food safety.

Employers and main employees are being asked to undergo intensive training. They should take no fewer than 40 hours a year of classes on the laws, regulations and ethics pertaining to food safety, according to the plan. Food safety inspectors are also required to undergo professional training for no fewer than 40 hours a year.

Food safety experts welcomed the program but doubted it could be implemented.

Sang Liwei, a food-safety lawyer in Beijing and a representative of the Global Food Safety Forum, a non-governmental organisation, explained: "Who will be responsible for calculating the time spent in the training?

"What happens if businesses find it's costly to invite experts and to provide training during work times?"

Mr Sang further suggested that giving timely warnings about food safety is as important as spreading information about food safety.

He added: "Local food safety committees can cooperate with mobile-phone services to promulgate warnings about food safety. Customers can then avoid eating questionable foods."