A pool at Auckland's Tepid Baths has tested positive for Legionella bacteria, forcing it to close temporarily.
The pool won't reopen until negative test results are returned, which will take two weeks.
A spa pool at the popular central Auckland public leisure centre was closed on February 11 following the detection of the bacteria.
The pool has been treated according to procedures recommended by the Auckland Regional Public Health Service (ARPHS).
A similar incident occurred at the Manurewa Pool and Leisure Centre in December.
As with the Tepid Baths, the pool was closed, treated and retested, and only reopened once a negative test was returned. Results from the second round of testing were received yesterday and remain negative.
The pools undergo regular testing for the bacteria.
Auckland Council's leisure manager Rob McGee says, "As this is the second event in a three-month period, we have taken the additional precautionary step of treating all 18 of our spa pools.
"On top of that, over the course of the next few weeks, we'll be working on a programme to ensure that every spa pool in the network undergoes an extra deep clean."
Mr McGee says that in both cases the team acted on advice from council's own Environmental Health team and ARPHS, closing immediately and treating the affected spa pools.
"Our current processes fully comply with or exceed New Zealand Standards, however if we can make any improvements to reduce the chance of the bacteria being present, we will.
"In the meantime, following the mitigation measures that we have already put in place and liaison with key parties, we are confident that the risk to public health is low."
Legionella bacteria can cause Legionnaires’ disease, which is caught by inhaling contaminated mist or vapour.
It can’t be spread from person to person.