Various types of precursor chemicals, used as raw materials to make the growingly popular synthetic drugs, present a new challenge to the anti-drug campaign, according to a senior police officer from Southwest China's Yunnan province.

The province, where the drugs seized usually account for 70 percent of the total in China, impounded a record 14 tons of drugs last year, up 45 percent from 2010, Meng Sutie, director of the provincial public security bureau, said in an interview last week.

Eight of the 14 tons were synthetic drugs, such as methamphetamine and ecstasy. The rest were traditional drugs such as heroin and opium.

By comparison, authorities seized more than 4 tons of synthetic drugs in 2010, and in previous years only a few hundred kilograms annually.

"Synthetic drugs are breaking in with tremendous force," Meng said. The synthetic drugs seized in Yunnan come from Myanmar, he added.

The province shares a 4,061-kilometer border with Myanmar, Laos and Vietnam, which together with Thailand make up the "Golden Triangle" of poppy cultivation.

Traffickers transported less opiates such as heroin and opium into Yunnan because of multinational crackdowns on poppy cultivation in recent years.

"Drug traffickers in Myanmar are turning to producing more synthetic drugs, which are easier to make for less money," he said.

Workers incinerate drugs and precursor chemicals confiscated by police in a furnace at a chemical plant in Kunming, Southwest China's Yunnan province, last year. More than two metric tons of drugs and precursor chemicals were destroyed that day. Lin Yiguang / Xinhua