Mexico's former top diplomat in Beijing says the Chinese authorities are doing little to stop the flow of precursor chemicals used to make the illegal drug methamphetamine, also known as Ice.
Southern China, particularly Guangdong, has been repeatedly pinpointed by the United Nations and international experts as a primary source of the chemicals ephedrine and pseudoephedrine needed to manufacture the addictive and increasingly popular drug.
However, the Chinese authorities were not interested in and did not co-operate on clamping down on the illegal export of the controlled chemicals, according to former Mexican ambassador to China Jorge Guajardo.
"Before I came to China, the first briefing I had with the [Mexican] attorney general was on the problem of precursor flowing from China to Mexico. It was the No 1 issue I had to address. However, we never got anywhere," said the former diplomat, who served in Beijing between 2007 and last year.
"When we sought assistance to stop the flow of precursor, there was no response from the Chinese side. There was never any assistance. The Chinese authorities always claimed it was a problem for Mexico's customs," he said.
Guajardo's claims are a marked departure from statements by Hong Kong and mainland Chinese authorities, who regularly say they are sharing intelligence and communicating with their foreign counterparts.
Guangdong is known to be a meth-producing powerhouse, with organised-crime gangs taking advantage of lax controls in the chemical industry to reroute controlled substances to the region and further afield.
A Sunday Morning Post report in January outlined how Hong Kong's triad societies trade precursor chemicals from the region for cocaine, guns and cash with Mexico's Sinaloa drug cartel.
Lufeng in Guangdong was the location of a massive bust late last year, in which authorities seized three tonnes of Ice and 23 tonnes of raw materials used in the production of the drug. The city has historic ties with Hong Kong's largest, richest and most organised triad, the Sun Yee On.
According to Mexican military sources, some of the illicit substances seized in the raid were destined for the infamous Sinaloa cartel.
"There was never any co-operation from the Chinese side and no intelligence sharing," Guajardo said. "It got to the point where all [Mexican] government officials visiting China had instructions to bring up the issue."
A report by the UN Office on Drugs and Crime in November highlighted the high risk of precursor chemicals being diverted in China. In 2012, Chinese authorities dismantled 228 meth-making labs, half of which were in Guangdong.
With an average purity of between 90 and 99 per cent, the Ice seized in Hong Kong and mainland China is of significantly higher quality than that in the rest of Asia, a fact that experts attribute to the prevalence of skilled chemists in Chinese drug- trafficking groups.
Questions sent to the Ministry of Foreign Affairs went unanswered yesterday.