Governor Linda Lingle issued a disaster declaration for the entire state, citing the damage to buildings and roads.
Ceilings collapsed at the main hospital in Kona on Hawaii Island. Hundreds were evacuated from damaged hotels on the island.
The quake's epicenter was at sea 10 miles north of Kailua - Kona, a town on the west coast of Hawaii Island, also known as the Big Island, said Don Blakeman, a geophysicist at the National Earthquake Information Center, part of the US Geological Survey.
Blakeman said there was no risk of a Pacific-wide tsunami, but there was a possibility of significant wave activity in Hawaii.
The US Geological Survey gave the quake a preliminary estimated magnitude of 6.6. The earthquake was followed by several strong aftershocks and dozens of smaller tremors. The aftershocks could continue for weeks, earthquake specialists said.
``We were rocking and rolling," said Anne LaVasseur, who was on the second floor of a wood-frame 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."
As many as 3,000 people were evacuated from three damaged hotels on Hawaii Island. Brad Kurokawa, Hawaii County deputy planning director, said the guests were being taken to a gymnasium until alternate accommodations could be found.
Water pipes exploded at Aston Kona by the Sea, an 86-unit condominium resort, creating a dramatic waterfall down the front of the hotel , said Kenneth Piper, who runs the front desk.
``We are a concrete building, but we really shook. You could almost see the cars bouncing up and down ," he said.
The quake caused widespread power failures, and phone communication was possible but difficult. By midday, power was restored to Hilo on the Big Island and was starting to be restored to Maui, said Chuck Anthony, a spokesman for the Hawaii National Guard . Some Honolulu neighborhoods also had power late yesterday afternoon, a spokesman for Hawaiian Electric Co. said.
