Seventeen cases have been detected in Bidyadanga, about 180km south of Broome in the Kimberley region, with the community placed into lockdown.
Kimberley Aboriginal Medical Services on Thursday said it had deployed a rapid response team from Broome to assist with testing and additional vaccinations.
It said 90 per cent of residents aged 12 and over were double dosed, with 10 per cent having received a booster.
WA Health said positive cases were being provided with care packages including meters to monitor vitals such as blood oxygen levels. Anyone who has been in the community since February 15 is being urged to present for testing.
Premier Mark McGowan said he expected further cases in the community.
"Bidyadanga is a large community ... it's nearly 1000 people so we expect more will follow," he told reporters.
"It's clear that cases are rising in the community. The mathematics are clear - we're not far away from recording over 1000 new cases per day.
"It's not a cause for panic but it's a reminder to take Omicron seriously."
Six cases have so far been recorded in the smaller community of Mantamaru, near the borders with South Australia and the Northern Territory.
WA has 2272 active cases and seven people are in hospital.
The state's third vaccination dose rate has surpassed 60 per cent and is on track to reach 70 per cent by the time the borders reopen on March 3.
The premier on Thursday announced a $67 million support package for businesses affected by the state's new public health restrictions.
It includes rent relief grants for business tenants and landlords, the waiving of licensing fees, and support for hospitality venues to create and expand alfresco service areas.
Mr McGowan said his government had spent $1.6 billion on supporting businesses during the pandemic.
With Perth's CBD streets visibly quieter in recent weeks, the premier urged people to continue working from offices unless instructed otherwise by their employers, and to keep attending hospitality venues.
"There's nothing to stop you from doing that," he said.
Figures released by the government this week showed 12 per cent of prison inmates had received their third vaccine dose.
More than two thirds of the children at Banksia Hill detention centre have not received a jab.
Opposition corrective services spokesman Peter Collier said it was putting an extremely vulnerable and marginalised cohort at risk.
Government minister Alannah MacTiernan told parliament a private medical provider had been engaged last week to undertake a mass vaccination program across all prisons.
She said vaccines had been available to all consenting adult prisoners since July last year and to youth detainees since November.
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