Bookings are now required for Covid-19 testing stations in Wellington run by Tū Ora Compass Health.
It told 1 NEWS it is no longer accepting walk-ups, while the Taranaki Street testing site is fully booked for the day.
The high demand for a test comes after a Covid-positive Sydney man's trip to Wellington over the weekend.
The Ministry of Health said of the 6999 tests carried out nationwide yesterday, 2100 alone were from Wellington.
This was five times the number taken on Tuesday.
The ministry said Healthline is currently experiencing a 20-minute delay on calls.
In the Wellington region, testing priority is being given to individuals who have been at a location of interest at the specified time and individuals who are symptomatic.
"At this stage, you do not need to be tested if you were not at a location of interest, unless you are symptomatic," the ministry said.
"It is critically important we are testing those who are most at risk from Covid-19 first. Anyone who was at a location of interest or is symptomatic should ring Healthline on 0800 358 5453 for advice on testing and how to book a test.
"People are asked to book in advance in for a test."
Confirmation of the man's positive test result came through late on Tuesday after he visited the capital over the weekend. He checked into multiple eateries and tourist hot spots around the city.
The case has seen Wellington moved into Alert Level 2 until at least Sunday.
A Capital and Coast District Health Board spokeswoman told 1 NEWS earlier that other testing sites across the region had capacity to take bookings and carry out testing.
"Please note that we are already strongly encouraging people to book appointments and to not present without an appointment," she said.
Testing locations in the Wellington region:
- Wellington Central, 196-200 Taranaki Street. Open until 6pm and will reopen at 8am tomorrow.
- Haitaitai Park, Ruahine Street. Open until 9pm and will reopen at 10am tomorrow.
- Wellington Regional Hospital, carpark by Te Hopai, off Mein Street. Open 1pm – 6pm and will reopen at 8am tomorrow.
- Porirua, 178 Bedford Street. Open until 9pm tonight and reopen at 8am tomorrow.
- Johnsonville, 24 Moorefield Road. Open until 4.30pm and will reopen at 9.30am tomorrow.
- Upper Hutt, Heretaunga Christian Centre, 51 Lane Street. Open until 4.30pm.
- Lower Hutt, 729 High Street. Open until 4pm and will reopen at 9am tomorrow.
- Kapiti, Coastlands Shoppingtown. Open 1pm – 5pm and will reopen at 12.30pm tomorrow.
- Karori, 11 Parkvale Road. Open 1pm – 5pm and will reopen at 1pm tomorrow.
- Wairarapa, located at various medical centres. Open standard business hours, and after-hour testing is provided at Masterton Medical Centre, 4 Colombo Road.