Giving for the first time their version of how an industrial chemical ended up being mixed into cough syrup and other medicines that reportedly killed at least 51 people in Panama last year, Chinese officials said Panama businesses, not Chinese firms, were chiefly responsible.

They also denied that the amount of diethylene glycol mixed into Chinese toothpaste that was exported to Latin America was harmful to health.

Diethylene glycol, an industrial solvent, was also the chemical found in Panama's tainted cough medicine.

Instead, officials in charge of ensuring the quality of China's food exports and domestic food safety hit out at what they called 'sensationalist' media reports for fanning fears over China's food and drug products.

Since March, reports on toxic pet food that have killed pets in the United States, tainted cough syrup and dodgy toothpaste - all containing substances originating from China - have put Beijing's problematic supervision of its food and drug industries under scrutiny.

Beijing is also anxious that growing international concerns over its produce and drugs could hurt exports.

The US has already moved to ban imports of Chinese toothpaste.

Mr Li Yuanping, a director-general of China's quality control watchdog, sought to quiet worries yesterday.

'China has a very good system for ensuring food safety, especially food for export,' he said.

He added that media reports, especially in the Western press, were 'playing things up'.

He disclosed statistics which showed that 99 per cent of China's approved food exports to the US from 2004 to 2006 had passed the mark, faring marginally better than food exports from the US to China during the same timeframe.

Mr Wei Chuanzhong, vice-minister of the General Administration for Quality Supervision, Inspection and Quarantine, also sought to downplay China's role in the Panamanian case.

In 2003, a Chinese manufacturer and a distributor sold 11,349kg of a chemical substance called 'TD' glycerine to a Spanish company, which in turn sold it to Panama traders.

Although the Chinese companies clearly indicated on export papers that the chemical was not for pharmaceutical use and had a one-year shelf life, they 'engaged in some misconduct' by mislabelling the product as 'glycerine' on their product packaging, said Mr Wei.

Glycerine is used widely as syrup in medicines, whereas TD glycerine - which contains 15 per cent diethylene glycol, a poison used to make anti-freeze - is not suitable for drug production, he said.

The Panama companies, however, 'changed the scope of use of the product to say the substance was medical glycerine that met US standards for use in medical products', he said.

They also altered the shelf life of the product, which had already expired, from one year to four years, he added.

'The responsibility here is very clear,' Mr Wei said.

Officials, however, promised to strengthen the regulation and the supervision of the manufacture, labelling and export standards of food and drugs.

As a warning to those who fail to comply, Beijing on Tuesday sentenced to death Zheng Xiaoyu, the former head of its Food and Drug Administration, for taking bribes from pharmaceutical companies.

Yesterday, Ms Yan Jiangying, spokesman for the administration, said Zheng's guilt did not mean China's entire food system was corrupt.

'We cannot question the integrity of the entire food administration system because of one person's crime. One man's crime doesn't mean the whole system is problematic,' she said.

tracyq@sph.com.sg