From the Associated Press:

"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 a possibility of 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. It was followed by several strong aftershocks, including one measuring a magnitude of 5.8, the Geological Survey said."

There are reports of casualties, but communications are difficult right now.