More than 20 Ministry of Interior and provincial police stormed a house in Pursat province yesterday, seizing nearly four tonnes of safrole oil, the biggest such cache uncovered this year, police said.

Safrole oil, a precursor to the production of MDMA, commonly known as ecstasy, was stored in 114 barrels in a dilapidated house in Veal Veng district occupied by Vietnamese-Cambodian Keo Thou, 29, who was arrested during the crackdown, district police chief Sam Some Oun said.

“Our police had been watching him for about one month before the raid,” Some Oun said, adding that 26 police officers had descended on the property at 6:30am yesterday.

Thou, who had long been suspected by local police of being involved in the illegal trade of safrole oil, was held for questioning last night.

Police were unsure whether he was working alone or had accomplices, Some Oun said, though it was suspected the safrole oil barrels were ultimately headed for Phnom Penh.

Officials also found machinery and large, heated vats to distill safrole oil not far from the house in the jungle at the base of the Cardamom mountain range that dominates the Veal Veng landscape.

Safrole oil can be illegally cooked in makeshift jungle stills by boiling the roots of trees in the sassafras family, which grow in the Cardamoms and along the Thai-Cambodia border.

On May 11, several people were arrested and more than 3,000 litres of safrole oil – enough to manufacture 30 million tablets of ecstasy – were seized during raids on six drug-producing sites in the capital.

According to Phnom Penh municipal police, who led that crackdown, investigators found the confiscated safrole had been imported by drug dealers across the porous Cambodian-Thai border.

Pursat provincial police chief Sarun Chanthy said yesterday’s raid had been the biggest safrole-oil bust this year.

“There is a government prohibition on refining or trading safrole oil. However, a number of suspects are still disobeying this prohibition despite a series of crackdowns,” Chanthy said.

Experts and anti-drug officials would examine the cache in coming days to determine whether it was being primed for illegal drug production, he said.

Pursat province Adhoc co-ordinator Phoung Sothea said the production of safrole oil in the jungle was difficult to crack down on, given the terrain of the Cardamoms.

“These suspects go deep into the jungle to find the location of [the sassafras trees],” Sothea said, adding that it was hardly ever Cambodians behind these operations, but more commonly Vietnamese drug traffickers.