Part of the coffee family, the leaf has been used for centuries in Southeast Asia and Papua New Guinea for its pain-relieving and mildly stimulating effects but it is now sold in powder form and exported worldwide — alarming some health regulators who have raised concerns about safety.

Kratom stimulates the same brain receptors as morphine, although it produces much milder effects.

"I take Kratom and have had no problems. Every strain has its benefits – some help you relax, others can treat insomnia or treat drug addiction. Some help increase stamina," grower Faisal Perdana told AFP.

Fellow farmer Gusti Prabu, who now exports 10 tonnes of the drug a month, agreed.

"Our ancestors used Kratom and there were no negative side effects. It can help eliminate drug addiction and help people detox," he explained.