The municipal health authority has launched a crackdown on restaurants' use of illegal cooking oil to improve food safety.

"All restaurants must retain receipts for cooking oil for inspection and we will increase the frequency of regular inspections," said Ma Yanming, press official of Beijing Municipal Health Bureau.

As part of the supervision process, licensed restaurants are already graded from A to D on sanitation and quality.

"We will concentrate more on C- and D-level restaurants by sending more inspectors and increasing the frequency of inspections," Ma said.

Starting Sunday, inspectors in all district branches of the health bureau are to visit restaurants daily to inspect receipts for cooking oil purchases and investigate supply channels, said Cai Changjing, publicity official of the Beijing health inspection office.

Restaurants are prohibited from purchasing cooking oil from illegal sources or buying oil products without having full information about the manufacturer. Violators will face penalties, and their cases will be referred to the public security department.

However, concerns have been raised about the scope of the campaign, which only covers licensed eateries and not illegal food carts.

"These food carts are major users of illegal cooking oil, but we are not responsible for that. Only urban management officers (chengguan) supervise them," Ma said.

METRO called the consultation hotline of the municipal bureau of city administration and law enforcement and was told that chengguan can confiscate unlicensed food carts and fine vendors 5,000 yuan ($770).

Food safety experts expressed doubt about the effectiveness of the campaign, since fake receipts are widely available.

"The seller's signature and an official seal of the oil company will be a more reliable way to verify the source of the purchased oil," said Sang Liwei, a food safety lawyer and the China representative of the non-governmental organization Global Food Safety Forum.

The campaign does not get to the root of the problem, he said.

"Even if this campaign prevents restaurants from using recycled oil, it does not stop people who are collecting and selling the illegal oil or threaten the livelihood of illegal factories," Sang said.

The crackdown follows media reports at the end of June that products sold as edible cooking oil in stores in Beijing, Tianjin and Hebei province are produced from so-called gutter oil and swill-cooked oil, which are left over from roasting ducks and other uses.

The Dongcheng district health bureau launched a crackdown against restaurants' use of illegal cooking oil since June 16. A total of 937 restaurants, snack bars and fast food restaurants have been inspected, with none found to be using illegal oil.