The 43-year-old helper arrived in Hong Kong on September 4 and had stayed at a hotel in Tsuen Wan.
She took five Covid tests during her quarantine and the results were all negative.
After completing her quarantine on September 25, she had stayed at her employer’s home at block 37 of Heng Fa Chuen in Chai Wan.
She tested positive for the virus on Monday. It is understood that she had a low viral load.
Tests also showed she had antibodies for Covid-19.
Authorities said the helper did not have any symptoms and had received two doses of the Sinovac vaccine before coming to Hong Kong.
The government has ordered anyone present at block 37 of Heng Fa Chuen, for more than two hours since September 25, to take a Covid test.
The helper also visited Victoria Park on October 1 and October 3. Anyone who was there, between 1 pm and 5 pm on these two days, must also take a test.
The government said as a precaution, those who have been fully vaccinated are also required to get tested.