All vessels must fully declare all cargo on board before docking at Hong Kong's port, according to the Hong Kong Customs authorities.
Generally, cargo in transit does not require an "import or export licence" as it will remain at all times on the ship. However, such a licence will be required for "certain type of strategic commodities", said a spokesman for the city's Customs and Excise Department.
So did APL, the container shipping firm contracted by the Singapore Armed Forces to transport nine armoured vehicles and military equipment back to Singapore from Taiwan, make a complete declaration of the sensitive cargo on board its vessel before it docked at Kwai Chung Container Terminals last Wednesday?
APL has declined comment as "the matter is pending discussion".
A report by Hong Kong's FactWire news agency claimed that APL did not have the "approval notice" for military vehicles.
Citing Customs sources, it said the shipment was first found not to possess the relevant permit at Xiamen's Haitian Container Terminals, where the vessel transited after leaving Kaohsiung in south Taiwan. The Xiamen Customs authorities also declined to comment when contacted.
The purported improper documentation apparently led to the seizure of nine Terrex Infantry Carrier Vehicles and associated equipment by Hong Kong Customs.
A retired captain who used to work for APL described the seizure as "a draconian move".
He told The Straits Times that it was not the first time an APL vessel carrying Singapore-bound military equipment had transited in Hong Kong.
"Hong Kong is quite strict when there's military equipment on board. It's not unusual for Customs officers to board the vessel to conduct interviews," he said.
"However, such cargo usually stays on board and is not forcibly discharged, like in the recent incident," he added, speaking on the condition of anonymity.
"With electronic submissions, any documentation lapse can be easily and quickly rectified. Moreover, APL has accumulated years of experience in transporting military equipment, including for the United States, not only Singapore."
The managing director of the Hong Kong Shipowners Association, Mr Arthur Bowring, told The Straits Times that this was not the first time that Hong Kong Customs had seized "sensitive items".
In 2010, it seized a disarmed K21 light tank and an armoured military carrier belonging to South Korea, apparently due to a missing Customs document. The vehicles were returned to South Korea through China's Ministry of Foreign Affairs two months later.