An Australian investigator has discovered there has been another death on board the massive coal carrier Sage Sagittarius, the third in the past six weeks.

In late August a crew member disappeared while the ship was sailing in international waters through the Timor Sea, 450 nautical miles north-east of Cairns.

The ship was ordered to dock at Port Kembla where an investigation was opened.

Days later, just before the ship arrived in Newcastle, another man died after falling down stairs.

New South Wales Police are still investigating that incident, and the latest death happened on October 6 while the ship was unloading in Japan.

An employee of the ship's managing company, Hachiuma Steamship, was killed after being crushed in a conveyer belt.

It is believed the Japanese employee boarded the Sage Sagittarius in Newcastle before it set sail to Japan to oversee crew safety.

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Dean Summers, from the International Transport Federation, says the latest death is highly suspicious as there was no mention of it for weeks.

Mr Summers says the incident was only discovered after an inspector in Australia found a note in the ship's log.

"A superintendent was put on there apparently to care for the welfare and safety of the crew. This is the superintendent that met his death just recently on October 6," he said.

"Today is October 29; if it was a workplace accident, I would have thought any capable authority would have been able to determine that's the case [by now].

"To our knowledge that hasn't happened and the case is still under investigation, and given the past two incidents, suspicious incidents, we cannot draw a conclusion either way."

Mr Summers is calling for a taskforce to be set up to investigate the deaths.

"We think there has to be a higher level coordination and today we'll be asking the Government to set up a taskforce to cut across the jurisdictions of the Australian Federal Police, the NSW Police and the Japanese police to make sure there is a transparent process to investigate the death of three seafarers," he said.

'Ships of shame'

Australian police say their investigation into the mystery over why there are so many deaths on this carrier is ongoing, but the author of a report which changed international shipping 20 years ago, says it is time the industry faced another investigation.

Known as Ships Of Shame, the report dealt with both dangerous rust-bucket ships causing occupational health and safety issues and also the way crews were treated.

Former federal minister for transport Peter Morris headed up the Ships Of Shame review.

He says the report was the catalyst for big improvements in the way international carriers were operated.

"The result of the report had quite a dramatic effect across the world and it was a major factor, I learnt afterwards, in improving the standard of operation of ships," he said.

He says what is happening on the Sage Sagittarius is a major concern and it is likely the crew are being pressured to keep quiet about the deaths.

"This is the kind of thing that we came across in the Ships Of Shame report back in 1992, where crew were intimidated into silence, where crew were starved, where crew were denied communication and obviously and people were just dead scared of telling anybody about anything," he said.

"Given the circumstances of this vessel, you certainly need an immediate investigation into what's happening with this vessel and then they can look beyond that to see what the ramifications are in respect of other vessels."

The Australian Federal Police and NSW Police say investigations into the first two incidents are ongoing.

The ship's managing company, Hachiuma Steamship, and its owner NYK Line were contacted for comment.