Reports of a low pitched humming in central Wellington have left the city council perplexed.
Wellington City Council has received around half a dozen complaints about the noise over the past few days, but say they have no idea what might be causing it.
Council spokesman Richard Maclean says staff haven't been able to identify the sound yet, but are keeping an ear to the ground.
"We're logging the calls and of course if they start to carry on incessantly then clearly we'll put our best people on the job to try and see whether we can actually figure out what's going on."
There was a similar mysterious hum in Auckland in 2006.
Scientists were contacted by more than 30 people, mostly in Auckland and the North Shore, who claimed to have heard a humming noise.
Dr Tom Moir from Massey University made a recording of the Auckland Hum and published it on the university's website.
Its cause was never found.
Mr Maclean is appealing for anyone who may have noticed the humming to report it to the Wellington City Council.