HONOLULU – A strong earthquake shook Hawaii early Sunday, causing a landslide that blocked a major highway on Hawaii Island and power outages across much of the state, authorities said.

The state Civil Defense had unconfirmed reports of injuries, but communication problems prevented more definite reports. Gov. Linda Lingle issued a disaster declaration for the entire state, saying there had been damage to buildings and roads.

The quake hit at 7:07 a.m. local time, 10 miles north-northwest of Kailua Kona, a town on the west coast of the Big Island, said Don Blakeman, a geophysicist at the National Earthquake Information Center, part of the U.S. Geological Survey.

Blakeman said there was no risk of a Pacific-wide tsunami, but there could be significant wave activity in Hawaii.

The Pacific Tsunami Center reported a preliminary magnitude of 6.5, while the U.S. Geological Survey gave a preliminary magnitude of 6.6. The earthquake was followed by several strong aftershocks, including one measuring a magnitude of 5.8, the Geological Survey said.

“We were rocking and rolling,” said Anne LaVasseur, who was on the second floor of a two-story, wood-framed house on the east side of the Big Island when the temblor struck. “I was pretty scared. We were swaying back and forth, like King Kong’s pushing your house back and forth.”

Betsy Garties, who lives in North Kohala on the northern tip of Hawaii Island, said she was lying in bed with one of her two young children when the quake struck. She first stood under a door frame as safety experts advise, then found that too wobbly for comfort and ran into the yard.

“It was strong enough that it was wobbling, so you almost lost your balance running out into the yard,” Garties said. “The house was visibly rocking.”

Airports were functioning despite the power outages, though travel was difficult and some flights were being canceled, officials said.

The last Hawaiian earthquake this strong struck more than 20 years ago. The magnitude 6.7 caused heavy property damage on Hawaii Island and collapsed trails into a volcano in Hawaiian Volcanoes National Park on Nov. 16, 1983.

The largest recorded Hawaiian earthquake struck the Ka’u District on Hawaii Island in 1868, causing 77 deaths. Its magnitude was estimated at 7.9.

A 9.5-magnitude earthquake, the largest in the world, struck Chile on May 22, 1960, and a tsunami traveled to Hawaii where 61 people died.

Associated Press writers Audrey McAvoy, Mark Niesse, and Jaymes Song contributed to this report.