Four deaths in the United Kingdom last week may be the latest in a rash of fatalities linked to a hike in an adulterated version of party drug ecstasy, a trend experts say goes all the way back to the jungles of Cambodia.

Rogue batches of synthetic MDMA-like substances have increasingly cropped up amid worldwide shortages of the common chemical precursor, safrole oil. The shortage is attributed to mass seizures of safrole in Cambodia from 2007 to 2009, when anti-drug officials attempted to eradicate clandestine production camps from protected forests.

“Cambodia is one of the main sources for economical extraction of safrole for the production of MDMA. The big seizure [in 2008] did cause an MDMA drought in Western Europe, which suggests that other sources of safrole were not available in sufficient quantity,” said Harry Shapiro, director of communications at UK-based drug research centre Drugscope.

Safrole oil, also known as sassafras oil, is distilled in Cambodia by boiling the roots and bark of a fragrant and rare tree known in Khmer as mreah prov mhnom. Manufacturing the oil involves felling several of the protected trees, which are found primarily in the Cardamom Mountain’s Phnom Samkos Wildlife Sanctuary in the western part of the country.

Though small-scale production of safrole oil for traditional remedies has been going on for centuries in Cambodia, experts say large-scale and highly profitable safrole production began around 2000, when international demand for MDMA peaked, and shortly after neighbouring Vietnam issued a ban on making the substance in 1999.

Production was ratcheted up further in 2004, soon after stricter controls were placed on the industry in China. In Cambodia, felling the trees and producing safrole became illegal in 2007, two years after Prime Minister Hun Sen ordered a crackdown on oil distilleries.

To strangle the elusive and destructive industry, conservation NGO Fauna and Flora International, the Cambodian authorities and the Australian Federal Police conducted high-profile raids on the remote production facilities, and in one go, netted 5.7 tonnes of safrole in 2008. The haul would have produced an estimated 245 million ecstasy tablets with a street value of nearly $8 billion. The same year, the National Anti-drug Commission reported seizing 35 tonnes of safrole-rich oils.

“We cannot allow any people or any company to extract safrole oil, it is too damaging to the forest. We have to protect the mreah prov trees,” said Meas Virith, secretary-general of the commission.

Similar seizures continued in 2009, when 5.7 tonnes were confiscated. And in 2010, 13,600 litres of seized safrole-rich oils were destroyed, but by that time, the drug industry had already moved on to synthesising alternative precursors.

“As a result of the strengthening of controls on the trafficking of the most commonly used precursors, illicit manufacturers have changed their approach,” said the UN Office on Drugs and Crime in a 2011 ecstasy report.

“Safrole is the precursor that everyone would like to get their hands on .  . . but when a drug precursor stops being available, a range of products move in as potential replacements,” said Laurent Laniel, a scientific analyst at the European Monitoring Centre for Drugs and Drug Addiction. “Traffickers started marketing a whole new range of substances as MDMA.”

Worldwide, the purity of the stimulant pills began to decline as the MDMA compound and its precursors were replaced or cut with other, cheaper or more readily available substances.

About half of ecstasy pills seized in the UK in 2009 contained no MDMA. A similar trend occurred in the Netherlands, where the number of ecstasy tablets containing no MDMA rose from 10 per cent in 2008 to 60 per cent by 2009.

New pills and forms of purported ecstasy started popping up, some mimicking stimulating and euphoric affects. Two of the most popular, known as PMMA/PMA and mephedrone, nicknamed “meow meow” or bath salts, started becoming popular through online sales shortly after “pure” MDMA became less available.

Police load a truck with seized safrole oil, used to produce MDMA, also known as ecstasy, during a raid in Phnom Penh in 2012. Photo Supplied

By May 2010, mephedrone had been detected in all EU states reporting to Interpol, as well as in Croatia and Norway.

“The appearance of mephedrone, and the ensuing legal and chemical chaos that is the so-called ‘legal highs scene’ can be traced directly to the UN’s burning of 33 tonnes of safrole in Cambodia in 2008,” said Michael Power, author of Drug 2.0. “The same thing happened in Thailand in 2010, but had less impact, as alternative precursors have now been found to safrole.”

However, alternative highs have had deadly consequences. PMMA and the semi-analogous PMA have led to deaths in England and Wales, Northern Ireland, Scotland, the US, Canada, Denmark, Norway and Australia.

Just last week, at the beginning of this year, four men in England who thought they were taking MDMA died with PMMA found in their blood stream, according to British media.

But safrole hasn’t disappeared. In Cambodia, seizures of safrole continue, albeit on a declining scale.

Last August, more than 3,200 litres of safrole oil were found stashed in 109 cases buried underground in Pursat.

“There's still oil coming through Phnom Penh,” said Toby Eastoe, Cardomom Mountains project coordinator for Conservation International.

Eastoe added that he’s not sure where or even if production is still happening. An aerial survey of the wildlife sanctuary revealed no stills or refineries, but that doesn’t mean they don’t exist elsewhere.

“After the seizures, it shifted so they’d log the mreah prov trees and take the logs out the forest like any other wood. The [safrole producing] factories could be located anywhere in the country,” Eastoe said.

The National Anti-Drug Commission insisted that safrole production was over, with “no more happening in Cambodia”, but conservationists said that’s unlikely to be the case.

“It’s too profitable,” said Tuy Sereivathana, country director of Fauna and Flora. ADDITIONAL REPORTING BY PECH SOTHEARY