West Australian Premier Mark McGowan has called for a pause on incoming travel from India and urged people to stop flying to the COVID-plagued subcontinent.
It comes as authorities investigate how two returned travellers contracted the virus while in quarantine at Perth's Mercure Hotel.
Genomic testing has revealed the virus spread from a couple who had returned from India to a mother and daughter from the UK who were staying across the corridor.
Mr McGowan will ask his national cabinet colleagues to consider seeking health advice about a freeze or reduction in flights from India.
He says the government has anecdotal evidence that people are returning infected with the virus after being allowed to fly from Australia to India.
Almost half of WA's cases in recent weeks had recently been in India, which is dealing with almost 300,000 new daily infections.
"We don't know why this is happening," Mr McGowan told reporters on Thursday.
"This is under the control of the Commonwealth - we don't control these things.
"Clearly, people shouldn't be going to India except for the most extreme of circumstances."
New Zealand implemented a temporary ban on travel from India earlier this month.
Mr McGowan warned that the number of cases in hotel quarantine was becoming unmanageable and that WA may consider seeking a future reduction in the weekly cap on international arrivals.
About 270 people have travelled from or through India to WA this month.
"We feel deeply for people who are in India but obviously it is a big risk to the broader community and to the integrity of our hotel quarantine system," the premier said.
Health experts believe a new "double mutant" strain - dubbed B.1.617 - is likely to be behind the surge in cases on the subcontinent.
WA authorities are closely monitoring infections linked back to the strain, which has also been detected in other countries.
"Our thoughts are with our friends in India at this difficult time, as well as with our Western Australian Indian community," Mr McGowan said.
"They are trying to put a stop to the third wave, however in Australia we need to do everything we can to keep this double mutant variant away."
The Mercure hotel will no longer accept international arrivals and the floor where the transmission occurred has been cleared of guests.
It will transition to a "low-risk" quarantine hotel for a flightload of seasonal workers expected to arrive from Tonga and Vanuatu next month.
Health Minister Roger Cook revealed that an internal review had found the Mercure was the highest-risk of the 10 quarantine hotels used in WA due to ventilation issues.
However, he said it had still been considered safe to accommodate all international arrivals with proper mitigation.
Other guests who stayed on the same floor at the same time were previously released from the hotel after testing negative.
They will be re-tested and directed to self-isolate until cleared. Security guards and healthcare workers from that floor are also being re-tested.
Two people who were in rooms immediately adjacent to the infected people have been asked to self-quarantine for 14 days.
One of those people has already returned a negative test.
