QUAKE CENTRE: The location of tonight's earthquake is marked with a star.
LATEST: A tsunami warning was issued as a precaution late last night after a earthquake measuring 6.6 on the Richter scale was felt across the lower South Island.
Civil Defence officials concerned by widely varying measurements of a big quake in Fiordland tonight said they were issuing a ''potential tsunami'' warning in Southland.
"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.
GNS Science reported the quake 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.
There were also reports of a second quake around 9.40pm, which was also felt in Wellington.
An Invercargill man said the quake lasted at least a minute.
"Things just started to rattle a bit, then the house started to sway."
He and his wife got their three young children out of bed and huddled under the dining table to wait it out.
Cracks had appeared around several door frames, he said.
Central Southland man Warren MacPherson said a hanging light in his house would have been swaying "a good six inches each way".
He was on the phone when the quake struck and rushed outside.
"By geez, there was a fair bit of movement," he said.
Invercargill police Inspector Olaf Jensen said there were no immediate reports of damage in the southern city, but the quake was significant enough to send staff into doorways.
He described it was a strong, rolling quake rather than a sharp jolt.
Neither the Manapouri Power Station and Tiwai Point Aluminium Smelter reported any damage.
Te Anau helicopter pilot Mark Deaker said he saw power lines arcing and sparks were flying in the air.
Fresh Choice supermarket owner Keith Cullen said 10 to 20 items smashed in each aisle of the supermarket.
A Queenstown resident living in a three-storey apartment said the building shook and swayed. ''Holy crap that was significant,'' the resident said.
The Pacific Tsunami Warning Centre in Hawaii issued the warning soon after the quake struck.
The centre said it was not known if a tsunami was generated, but it was issuing the warning based on the earthquake evaluation.
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