The suitcases released a strong stench when opened. Inside was 790kg of ivory that had been fashioned into raw and semi-finished products and was covered with large quantities of dried blood.
In an apparent effort to avoid detection, the men and women aged 20 to 54 had flown from Angola to Hong Kong via Ethiopia and were to have flown on to South Korea before finally reaching Cambodia.
Ng King-hong, head of Customs and Excise airport command, said the 15 transit passengers, none of whom spoke English, Cantonese or Putonghua, seemed "surprised" at being arrested.
Tom Milliken from Traffic, a network which monitors wildlife trade, said finding such a haul hidden in passengers' luggage was unprecedented.
He believed the ivory was ultimately bound for the mainland, for which Cambodia serves as a conduit for the illicit trade.
Chops were among the unfinished products in the cases, along with bangles and prayer beads. Milliken said this indicated that the haul was bound for the mainland. "I'd say this was destined for the Chinese market because of the name seals - they are not commonly found on the Thai market," he said.
"Angola makes sense [as the source] because it is one of the largest-worked ivory markets in Africa," he added.
Wild Aid executive director Peter Knights said it was a "much-needed crackdown" to deter the current high levels of ivory smuggling.
But he added that these efforts "would be greatly facilitated by a total sales ban on ivory".
Hong Kong for Elephants co-founder Alex Hofford said Vietnam and Cambodia, not just mainland China, were rapidly emerging as ivory consumption hotspots in their own right.
The arrests follow the destruction of the first batch of the government's 30-tonne stockpile of illicit ivory last month, and the newly seized ivory will be added to the pile to be destroyed.