The three cases are all members of the one family who had been staying on the 12th floor of the Adina Apartments Hotel at Town Hall.
The infections were initially listed as being overseas acquired but have today been reclassified by NSW Health.
An investigation was launched after the trio tested positive to the same viral sequence of COVID-19 as a family of four staying in an adjacent room of the hotel, despite having travelled from different countries on different days.
The original family of four is believed to have been infectious for four days while staying at the hotel – from Thursday, April 8 through to Sunday, April 11, when they were moved into Special Health Accommodation.
There have been no new COVID-19 cases detected in NSW today outside of the hotel quarantine system.
Six cases, further to the three re-classifications, were found inside the hotel quarantine system.
It brings the total number of active cases in New South Wales to 67, including one person who is seriously ill in ICU.