The spokesperson did not state how many guards were in isolation, but Ian Rintoul from the Refugee Action Coalition said he believed dozens of employees had attended a work function at the hotel during the first weekend of July.
The confirmation came hours after a spokesperson from the Department of Home Affairs said a worker at Melbourne's Mantra Hotel, which houses detained asylum seekers, had tested positive for coronavirus.
The employee had tested positive on 8 July after developing symptoms the previous day, the spokesperson said.
"Everyone is panicking ... It's like a cruise ship in here. If anyone catches this virus, all of us could get it," asylum seeker Mostafa Azimitabar told SBS News. Detainees were informed of the positive case on Sunday.
Advocates and politicians have raised concerns over the potential for COVID-19 to spread in immigration detention for months, including Labor MP Ged Kearney, whose electorate covers the location of the Mantra Hotel.
"They could have moved the men into the community to minimise the risk. They did not," she said.
The Queensland Government on Monday issued an urgent health notice calling on people in the state who visited the venue between 3-10 July to self-isolate.
People in Australia must stay at least 1.5 metres away from others. Check your state’s restrictions on gathering limits. If you are experiencing cold or flu symptoms, stay home and arrange a test by calling your doctor or contact the Coronavirus Health Information Hotline on 1800 020 080. News and information is available in 63 languages at sbs.com.au/coronavirus.