A powerful earthquake jolted Alaska panhandle residents out of their sleep early Monday, but no significant damage was reported, authorities said.

The quake happened at 1:50 a.m. Alaska time (5:50 a.m. EDT) and was centered beneath the ocean off the southern end of the panhandle, said Bill Knight, a scientist at the Alaska Tsunami Warning Center (search) at Palmer. The center had calculated a preliminary magnitude of 7.0 but the U.S. Geological Survey (search) later put the magnitude at 6.7.

The jolt, capable of significant damage had it happened near populated areas on land, did not generate a tsunami or seismic sea wave (search), Knight said. Callers to the center reported only "items falling off shelves," he said.

"We're pretty lucky, I guess," said James D. See, police chief in Craig, a logging and fishing town about 60 miles northeast of the epicenter. A 6.1 magnitude temblor had shaken the town last July 12.

See said the quake, which seemed to last about 20 seconds, woke him up and knocked a picture off the wall but caused no other damage in his house.

Residents deluged police with calls. Nobody reported damage to buildings but some effects may be evident only after daybreak, See said.