The rest of the country will move to alert level 2 at midday - until midnight on Friday.
Margie Apa, Northern Region Health co-ordination centre lead (and Counties Manukau Health CEO) urged Aucklanders to remain vigilant, remain calm and follow public health advice.
"This news is of concern, but we expected to see further community cases in Auckland at some point in this pandemic, and we are well prepared," she said.
"We are working closely with the Ministry of Health and other agencies to ensure everything possible is done to contain the spread of Covid-19 in our communities."
Anyone with symptoms of Covid-19 - such as a new or worsening cough, sore throat, runny nose, fever, temporary loss of smell and difficulty breathing - should be tested.
"Our message to people living in Auckland is to continue to be vigilant," Apa said.
"The best defence against Covid-19 is to follow the same actions we took earlier in the pandemic. Maintain good hand hygiene.
"If you are sick, stay home. Keep track of your movements to help us with contact tracing. Maintain physical distancing."
Two pop-up centres will be open in Auckland from 9am Wednesday.
One of those is in the Otara Town Centre car park (14 Fair Mall, Otara), the second is at Health New Lynn (Level 1 car park, Totara Health Services, McCrae Way, New Lynn).
Apa said the health sector in Auckland was well prepared to respond to new community cases but asked Aucklanders to prepare to be patient if they were aiming to be tested today.
All health services are regarded as essential and should continue as usual, with an additional focus on infection prevention control measures and distancing of patients, she said.
"Hospitals will continue with planned care including clinics and surgery – patients should keep their appointments unless advised otherwise by their specialists.
"The city's hospitals and aged residential care facilities are updating their visitor policies and other protocols to protect the most vulnerable."