Travelers returning to New Zealand will face stricter rules at quarantine hotels as health authorities investigate how up to three people got infected with the coronavirus while isolating at Auckland’s Pullman Hotel.

The people were released before testing positive and were potentially contagious, but so far testing has shown no evidence the virus has spread in the community. New Zealand has managed to stamp out community transmission of the virus.

COVID-19 Response Minister Chris Hipkins said Thursday that as an interim measure, travelers would need to stay in their hotel rooms for the final days of their 14-day mandatory quarantine, and would also face stricter controls around leaving their rooms at other times.

Health authorities believe the three people at the hotel caught the virus from another returning traveler, who had the South African variant.

Meanwhile, Australia has extended its suspension on quarantine-free travel from New Zealand for another three days. Australia is requiring New Zealanders to quarantine for 14 days in hotels upon arrival.