Air pollution from traffic has soared to levels higher than before the level 4 lockdown in Auckland.
NIWA recorded increases in nitrogen oxide levels, which are mostly caused by road traffic exhaust, at three sites in the city, partly driven by light winds.
NIWA air quality scientist Ian Longley said despite some restrictions easing under level 3, the figures for the past two days are surprisingly high.
"That does imply to me that a lot more vehicles have hit the roads again than certainly I was expecting."
Today's nitrogen oxide level at Takapuna was 250 mg/m, which according to NIWA has not been as high since August last year.
Similar levels were recorded at Henderson and Penrose, while levels were still lower in Queen St.
Nitrogen oxides have also returned to pre-lockdown levels in Christchurch, NIWA said.