"We've had big differences in the measurements of the quake , ranging from 6.6 by GNS Science, to 8.2 by a tsunami warning centre in Hawaii - we're issuing a precautionary message," said an emergency management spokesman in Wellington, Vince Cholewa.Mr Cholewa said the initial United States Geological Survey measurement used by the Hawaii tsunami centre was quickly downgraded to 7.8 magnitude.
"GNS and the USGS are working through it," he told NZPA.
There were no immediate reports of casualties or major damage from the quake.
GNS Science reported it struck at 9.22pm quake, centred 90km southwest of Te Anau.
It was felt strongly by residents in Invercargill, Dunedin, Timaru and as far north as Wellington.
An Invercargill man told NZPA the quake lasted at least a minute. (NZ.News.Yahoo)
