'It was a violent shake'

Los Angeles, California (CNN) -- Officials expect to have power fully restored by Sunday afternoon following a 6.5-magnitude earthquake which struck off the coast of northern California Saturday, leaving thousands without electricity.

The quake, which ran about 13.5 miles deep, hit at 4:27 p.m. Saturday, about 33 miles from the coastal city of Eureka, according to the U.S. Geological Survey.

Nearly a dozen aftershocks followed, the strongest at 4.5 magnitude. They continued into the early morning hours Sunday.

As of 7 a.m. Sunday, about 500 customers were still without power, said David Eisenhower, spokesman for Pacific Gas and Electric Company. The company hopes to restore power to those remaining customers Sunday, hopefully by the afternoon, he said.

The company was launching helicopters Sunday morning to patrol for gas leaks at the transmission lines that run through remote areas, he said, adding there have been no reports of such leaks.

As of Saturday night, the company said 28,000 customers, most in Humboldt County, were without power. Most had their lights back on by late Saturday night.

There were no reports of serious injuries or damage.

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St. Joseph Hospital in Eureka said it treated several people for minor quake-related injuries, but none were significant enough for the patient to be admitted.

Chris Durant, a reporter for the Eureka Times-Standard, said he was working on the second floor of the newspaper's concrete building when he and his colleagues felt the earthquake.

"We are used to feeling small ones," he said, "but after the first few seconds, we looked at each other and said, 'This is not a small one.'"

Eureka resident Cole Machado told CNN he was talking on the phone when he felt the ground shake. "I thought my TV was going to fall over."

Tom Grinsell, the fire chief in the nearby town of Ferndale, said it was "one of the strongest quakes I remember in quite a while. I assumed it was going to be a lot worse than we're seeing."

He said the quake had a "strong shaking to it and was rather lengthy."

Grinsell said his department has received numerous calls about broken glass, emptied shelves, and stucco and plaster knocked off walls. He added that the damage is cosmetic and that no buildings have collapsed.

Grinsell said officials have asked residents to stay off the roads because of debris, and to conserve water until it's certain there is no damage to the water system.

Ferndale resident Jessica Stephens Tucker described the movement from the temblor: "It rolled and rolled and then it slammed."

Dave Magni, owner of the Ivanhoe Hotel in Ferndale, said, "We are sitting in a sea of booze" after the quake.

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A 6.5-magnitude quake is considered "strong", said CNN meteorologist Jacqui Jeras, who noted that about 120 earthquakes of that strength are recorded worldwide each year.

CNN's Dina Majoli, Nick Valencia, Steve Brusk, Samira Simone, Leslie Tripp and Greg Morrison contributed to this report.