Beijing health bureau has carried out a citywide inspection of oil used in the catering industry after media reports claimed some hazardous oil produced from duck roasting has been reused in barbecue stands.

The one-week inspection, which started on Wednesday, targets local restaurants, aims to make sure cooking oil in restaurants is bought from qualified producers and leftovers go to licensed oil recycling companies.

As many as 276 restaurants had been inspected by 4 pm on Wednesday and no duck oil was found in food production.

"Three restaurants couldn't offer invoices for the oil they bought, which is against our regulation. We have confiscated the 6 kg of untraceable oil," Ma Yanming, the bureau's press official told METRO.

Around 130 of the 276 restaurants tested are running roast duck businesses and another 10 are barbecue restaurants. According to Ma, all restaurants should keep records about where they buy oil from and who they give the leftovers to.

"It is difficult for us to crack down on illegal duck oil users as they are usually small companies that don't have a stable location," Ma said, adding those who use the oil are mostly lacking sanitation permits from the health bureau.

Ma urged all Beijing residents to stop eating at unlicensed food stands.

"If people stop eating there, the market for such oil will shrink and probably disappear," he said.

However, a CCTV report claimed all six roast duck producers in three farm-produce markets near the South Second Ring Road and West Third Ring Road were selling discarded duck oil to food makers at 6 yuan or 7 yuan a kilogram.

The program said the oil is often sold from Beijing roast duck producers to barbecue stands, steam bun shops and canteens for construction workers.

Many health experts said that, due to the high temperature when a roast duck is prepared, cancer-causing agents can be produced. As a result, reused oil can pose a danger to people's health.

However, Ma Yanhua, director of development with the China Cuisine Association, said the effect of reused duck oil is under investigation and they will release more details as soon as they have them.

Ning Hao, director of operations management with renowned Peking duck maker Quanjude, said its 11 stores in Beijing produce 250 kg of oil every day. The company uses a licensed kitchen waste company to handle the oil to avoid it getting back onto the market.

The Erqing branch of Beijing Environment Sanitation Engineering group, which began in 2007, is the first and largest company in Beijing to handle kitchen waste.

Wang Baogui, director of its business department, said they have around 300 clients across the city, mostly large restaurants, hotels and universities.

"We pick up their kitchen waste, transport and then process it for free," he said.

Jiang Qi, who frequently visits barbecue stands with his 5-year-old son, expressed his concern.

"I've never paid attention to their oil or whether they have a sanitation permit," he said, adding he visits food stands three or four times a week in the summer.

"I just pick the most popular one. I will never take my son there again," he said.