The Australian Border Force has confirmed a staff member at the Christmas Island detention centre has tested positive for COVID-19.
It is the second of two cases recorded there this week — the only infections since the pandemic began in 2020.
The ABF confirmed the case late on Friday, along with four cases among staff members at its Yongah Hills Detention Centre in Northam, Western Australia.
The immigration service said it was not aware of any cases among detainees.
About 1,600 people live on the island, plus about 200 in detention.
Shire of Christmas Island president Gordon Thomson confirmed there were two cases and said the hospital was equipped to handle some treatment of COVID-19 but did not have ventilators.
He is worried about the virus spreading in close-knit communities.
"I'd say half of our population is housed in those close contact units, which does cause some concern to people," Mr Thomson said.
Rules similar to WA
Mr Thomson said the administrator of the federally governed island had put rules in place that were similar to those in WA.
He said the Union of Christmas Island Workers wrote to the administrator on February 25 requesting only residents and essential workers be allowed to visit.
Mr Thomson said that request was not granted, meaning anyone could visit the island under providing they returned a negative rapid antigen test.
They must also take a test on their third day in the community.
Mr Thomson said he understood the need for consistency in travel restrictions, but he was concerned about the community.
"It could be quite devastating," he said.
"If we don't observe some of the rules of caution, which are that you restrict travel — you restrict the travel of the spread of the virus.
Pub patrons told to isolate
According to notices distributed by the Indian Ocean Territories COVID-19 subcommittee, the Christmas Island Pool Hall was deemed a high-risk exposure site after a positive case visited there on March 5 and 6.
"It has been reported that masks were not being worn appropriately in the pool hall by many patrons, which is disappointing and has increased the level of risk," the notice said.
Another case arrived on a flight on March 8 and tested positive the next day.
People who were at the pub during the exposure times were told to quarantine immediately.
The ABF says "standard department protocols" are being followed, including contact tracing, quarantining, testing and cleaning at the detention centres at Christmas Island and Northam.
"The ABF's priority is the health and safety of detainees and staff," a spokesperson said in a statement.
Medical services inside the detention centres are provided by contractor International Health and Medical Services.