Sixteen buses have been ordered off Wellington streets after safety faults were found during inspections.
Police and the Transport Agency spent Wednesday examining buses to check that faults identified in May, when 11 buses - or nearly 10% of the city's fleet - were ordered off the roads had been fixed.
But police say the situation appears to have got worse, with buses pink-stickered for leaking flammable fluid, having loose battery boxes and doors that shut with too much force.
They say there is still another day of inspections to go and more pink stickers are likely.
NZ Bus chief executive Zane Fulljames says there were a larger number of inspections than in May and the issues found were minor in nature.
Mr Fulljames says the oil leaks are actually oil weeps ... "less than half a cup of oil".
He says all the company's vehicles have fire suppressant systems and the company has clear safety procedures and guidelines.
Mr Fulljames says the company has enough spare buses to cover any shortage while vehicles are off the road.
Wellington Regional Council had advised people to check on the Metlink website or with the call centre, saying it did not know which routes and services would be affected on Wednesday evening.