The haul of heroin that the North Korean drug ship Pong Su brought to Australia was a knock-off brand, Australian and US law enforcement agencies believe, carried in packaging that falsely suggested it came from the "Golden Triangle".

Samples from the 125 kilograms of high-purity heroin seized by Australian Federal Police in 2003 along the Great Ocean Road town of Lorne were sent for analysis at Australia’s National Measurement Institute and the US Drug Enforcement Administration’s laboratory.

But agencies had never before seen that type of heroin making it highly likely it was refined by North Korean chemists.

Episode eight of The Age and Sydney Morning Herald’s podcast, The Last Voyage of the Pong Su, examines the ongoing mystery over the origin of the heroin on board the ship.