UPDATED: Western Australia Premier Mark McGowan has placed the Perth, Peel and South-West regions into a five-day lockdown until Friday.
Mr McGowan has revealed a male security guard in his 20s has tested positive for COVID-19 after working at a quarantine hotel.
Mr McGowan said the man worked on the same floor as a person positive for the UK variant of COVID-19 and he reported in sick on January 28 after working 12-hour shifts the previous two days.
The man and his household members have been placed in hotel quarantine and close contacts are being contacted.
But Mr McGowan said there remained a concern that the UK variant could be in the community.
Mr McGowan said school holidays would be extended until next week to match the lockdown and he encouraged anyone visiting those areas stay where they are for the week.