A Bangladeshi man and a decomposing corpse were found in a container at Pasir Panjang Container Terminal on Sunday night.
Dock workers heard banging sounds coming from the container, which had been there since late last month and had been believed to be empty.
When they opened it, they were shocked to find a Bangladeshi man alive and desperate to get out due to the foul stench from his companion's decomposing corpse.
The container supposedly came from Bangladesh with the two men in it and was dropped off at the port here.
The Straits Times understood from dock workers that all containers from Singapore are put through a scanner before being transported into the port, while containers from other countries might not undergo that process.
What was surprising was that these containers were sealed and it would have been impossible for anybody to get into them.
PSA Corp, which manages the port, told the same paper that the incident is being investigated by the police.
At around 8:20pm on Sunday, the container was being moved onto a trailer to be reloaded onto a ship sailing to Vietnam. However, to the surprise of the trailer driver, he heard faint banging noises coming from inside.
When the container was opened, the stench from the decomposing body was so strong that dock workers had to move away from it.
The deceased man was in his 40s, and was pronounced dead by paramedics at about 8:50pm, said a police spokesman.
Chinese evening paper Lianhe Wanbao reported that, from the state of decomposition, he could have been dead for more than four days.
There was nothing else in the container apart from the two men.
The other man, who is in his 20s, was taken to Alexandra Hospital and is assisting police with investigations.