By Tom Westbrook and Charlotte Greenfield
SYDNEY/WELLINGTON (Reuters) - A powerful 7.8 magnitude earthquake struck off the Solomon Islands early on Friday, but there were no immediate reports of casualties and a tsunami warning for a wide swathe of the South Pacific was later lifted.
Solomon Islands National Disaster Management Office director Loti Yates said he received reports of collapsed buildings on Malaita, an island near the epicenter of the massive undersea quake, which had initially prompted a tsunami watch as far afield as Hawaii.
"Most houses are built by traditional materials, so some houses are reported to have been damaged in south Malaita but the extent is not known," Yates told Reuters by telephone.
He said several villages had evacuated to higher ground, but that there were no reports of deaths. A helicopter had been sent to survey the damage at Malaita, which is home to about a quarter of the Solomon Islands population of 600,000, Yates added.
The U.S. Geological Survey downgraded the quake, which struck at 4:38 a.m. local time (12.38 p.m. ET Thursday), to magnitude 7.8 from an original reading of 8.0. It put the depth at around 40 km (25 miles).
The U.S.-based Pacific Tsunami Warning Center (PTWC) had issued warnings for the Solomon Islands and neighboring island chains of a potentially hazardous tsunami, but a couple of hours after the quake it said the threat had passed.
An initial tsunami watch alert for Hawaii had earlier been canceled. Authorities in New Caledonia ordered people on the east coast and in the Loyalty islands to move to higher ground.
The Solomons, perched on the geologically active "Pacific Ring of Fire", were hit by a devastating tsunami following an 8.1 magnitude quake in 2007. At least 50 people were killed then and dozens left missing and more than 13 villages destroyed.
In 2013, a quake set off a tsunami which killed at least five people in the chain of more than 900 islands, the site of several major battles during World War Two.
John Pirimare, a resident on Nafinua Island, spoke to Reuters from up the hills where he evacuated immediately after the quake with around 500 to 600 villagers after they received the tsunami warning on their phones.
"It was a great shock but no serious damage," Pirimare said. "Most of the people went straight here; and we won't leave until the tsunami threat has passed."
James Samani, duty manager at the Solomon Kitano Mendana Hotel in the capital Honiara, said the earthquake was strongly felt but the hotel was not damaged.
"We felt it big and strong in Honiara, but at the moment here in the hotel all the guests are in the lobby," Samani told Reuters.
Australia said there was no risk to its coastlines. New Zealand canceled a marine and beach threat warning.
(Additional reporting by Jane Wardell, Byron Kaye, Jonathan Barrett, Swati Pandey; Writing by Byron Kaye; Editing by Alex Richardson and Lincoln Feast)