LIVE: USGS holds briefing after magnitude 7.0 earthquake strikes Northern California

SAN FRANCISCO — USGS says that a magnitude 7.0 earthquake has hit Northern California in Humboldt County.

A tsunami warning has been issued by the National Weather Service.

It was initially reported as a 6.6 quake but then was upgraded by USGS.

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There were no immediate reports of any damage.

The earthquake was felt as far south as San Francisco, where residents felt a rolling motion for several seconds. It was followed by smaller aftershocks.

There is a major delay in the Bay Area’s BART transportation system due to the quake. There’s no train service though the underwater Transbay Tube.

At least 5.3 million people in California were under the tsunami warning, the U.S. Geological Survey said in a yellow alert, which predicted localized but minimal damage.

More than 1.3 million people lived close enough to the quake that they could have felt it, the USGS estimated.

In the Santa Cruz area, phones buzzed with a tsunami warning from the National Weather Service that said: “A series of powerful waves and strong currents may impact coasts near you. You are in danger. Get away from coastal waters. Move to high ground or inland now. Keep away from the coast until local officials say it is safe to return.”

This is a breaking news story. Check back for updates.

The Associated Press contributed to this report.