A group of Sydney dock workers are sweating on the results of coronavirus tests after boarding a ship now found to have been carrying infected sailors.

The Inge Kosan, an LPG tanker, was docked in Port Botany for a day from March 31 after arriving from the Papua New Guinea capital of Port Moresby.

It sailed for Vanuatu on April 1.

“Health authorities in Vanuatu have confirmed that 12 out of 13 crew members from the ship, including [a] deceased crew member, tested positive for COVID following testing in Port Vila,” NSW Health said on Friday.

Some 15 wharfies boarded the vessel when it was at Port Botany more than three weeks ago and six tested negative for COVID-19 on Thursday night.

The remaining nine are awaiting their results, which are expected on Friday.

NSW Health said none of the crew of the Inge Kosan left the ship when it was in Sydney and the wharfies who boarded it had worn protective gear.

“Procedures were in place to support COVID safe practices in ports, including on vessels,” NSW Health said.

“Further investigations are ongoing as to whether an additional three workers also boarded the ship.”

PNG is in the midst of an outbreak of COVID-19 that has already led to the deaths of more than 90 people.

Meanwhile, NSW authorities are still trying to locate four people who may have been exposed to COVID-19 at a Sydney quarantine hotel.

Up to 40 returned travellers and some hotel staff may have been exposed to the virus earlier this month.

NSW Health has contacted 36 of those people and is urgently trying to find the other four.

The potential quarantine breach was revealed Wednesday night after three returned travellers who stayed at the Mercure Hotel in Sydney were diagnosed with the same South African strain of the virus.

The travellers were family members who had stayed in connecting rooms on the 10th floor of the Mercure Hotel, while the third person stayed in another adjacent room.

NSW chief health officer Kerry Chant said some hotel guests had since travelled to other states and territories and authorities there had been alerted.

Victorian health authorities identified six people as close contacts linked to the Sydney hotel and said they will be tested on Thursday.

Anyone who stayed on the 10th floor of the Mercure between April 7-12, should get tested and self-isolate until 14 days after they left quarantine.

Staff potentially exposed will also have to self-isolate.

Authorities are still investigating how the breach occurred.

A separate case of transmission between hotel rooms at the Adina Apartment Hotel at Town Hall is ongoing, and all contacts located so far have tested negative.