Corruption within China's pharmaceutical industry is a key factor in Guangdong province becoming the production centre for the burgeoning global trade in crystal meth, a top United Nations drugs official said. Speaking in the wake of a massive seizure of the powerful stimulant near Lufeng district earlier this month - one of the biggest ever in Asia - senior UN drug official Jeremy Douglas said the quick and easy access to precursor chemicals required to make crystal meth clearly pointed to "corruption in the pharmaceutical and or chemical industries'' in the mainland. Douglas was briefed by Chinese officials in the immediate aftermath of the bust in which 2.4 tonnes of methamphetamine - known as Ice in Hong Kong - was seized. His assertion comes amid President Xi Jinping's ongoing drives against graft and drugs, and follows UN pledges to strengthen co-operation with Beijing and others in the region in the fight against drug gangs and the corrupt networks that underpin them. "To operate a lab like this, you need a lot of chemicals, which are legitimate, regulated chemicals from the pharmaceutical industry," Douglas said. "This group has been able to get their hands on the precursor chemicals necessary to produce the drugs. They've been doing it for a long time, which means they're getting these chemicals on a regular basis. "There is some kind of corruption in the chemical/pharmaceutical industry taking place allowing this to happen." Meth can be manufactured using a variety of chemicals - most notably ephedrine and pseudoephedrine, which are also used in cold and flu medicine. The latest seizure follows the January arrest of Hongkonger Wong Chi-ping - suspected of being a major drugs kingpin in the region - in Indonesia during a raid that netted 860kg of Guangdong-manufactured meth. Last November, 400 tonnes of chemicals seized before they could be turned into meth were destroyed by police in Lufeng. Lufeng is a traditional heartland of Hong Kong's largest triad, the Sun Yee On. Of the latest haul, Douglas said: "It was most likely bound for a whole variety of destinations within and outside China." Hong Kong officials said a record number of drugs busts at the airport last year was due to "enhanced enforcement and intelligence" - not increased trafficking activity. Shenzhen authorities captured 4.2 tonnes of narcotics in November and arrested 5,000 people, a number of whom were involved in drug trafficking to Australia via Hong Kong. And in June, the meth trafficking issue was believed to have been on the agenda when Secretary for Security Lai Tung-kwok met ministers in Australia and New Zealand.