There is no management plan for the vessel until official clarity on results.
Medical teams boarded the docked ship on Monday, taking extra precautions on the bulk-carrier.
Australian Medical Association WA President Dr Mark Duncan-Smith says if an outbreak was to spurr from this, it would leave the hospital system in a difficult situation.
"We're very concerned. Our medical system is on it's knees without COVID. If COVID gets out into the community, especially the Delta variant. that could be a big crisis."
Elsewhere, Premier Mark McGowan has called for fresh modelling in relation to NSW's rising case numbers.
WA Health is monitoring four active COVID-19 cases who are all currently in hotel quarantine.
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