Premier Mark McGowan has confirmed that six people aboard the Al Kuwait livestock vessel have tested positive for COVID-19.
The State Government fears that due to a lack of ability to self-isolate, further crew members may fall ill to the virus.
“We suspect it is more than likely more crew members may become infected with the virus,” Mr McGowan said.
“This is an extremely concerning situation that we find ourselves in.”
The news comes after the state enjoyed yet another spell without infections – four days – thanks in part to its strict approach to border patrol.