Kosaku Monji, 37, was on the Sage Sagittarius on October 6 when it was unloading a cargo of Newcastle coal in the Japanese port of Kudamatsu.

It arrived back in Newcastle on Thursday and is loading coal on Kooragang Island.

International Transport Workers Federation (ITF) spokesman Dean Summers said Mr Monji had apparently been crushed to death in a conveyor belt.

‘‘His death, like that of the two seamen before him on the Sage Sagittarius, is highly suspicious,’’ Mr Summers said.

‘‘To make matters worse, we only discovered it by accident today when we read a brief reference to it in the ship’s log,’’ Mr Summers said.

He said a dedicated federal taskforce was needed to investigate the three deaths, which were a blight on Newcastle’s reputation, given the regular visits the Sage Sagittarius made to the port.

The federation raised the alarm on the Sage Sagittarius after its Filipino chief cook, Cesar Llanto, 42, disappeared off the Queensland coast on August 30.

Two weeks later,  on September 14, the ship’s chief engineer, Hector Collado, 55, died in Newcastle.

Ambulance officers called to meet the ship as it docked at Carrington were unable to revive Mr Collado, who was also a Filipino.

He was described at the time as having serious injuries.

Mr Summers said the rest of the crew were ‘‘scared and traumatised’’ and the ITF asked the shipping company to send them home.

‘‘We have since learned they were sacked when they got there,’’ Mr Summers said.

A spokesman for ship owner Nippon Yusen Kaisha said the company’s Newcastle and Sydney staff had been told by the Tokyo head office to co-operate with investigators.

An Australian Customs Service spokesman said an inspection of the ship this week was routine and unrelated to the deaths on board.

NSW Police said investigation were continuing.