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

The epicenter is off the coast near Petrolia, in Humboldt County, the USGS said.

Also, a tsunami warning that had been issued for coastal areas in California and Oregon, including San Francisco, was canceled just before noon local time.

"The tsunami Warning is canceled for the coastal areas of California and Oregon," the National Tsunami Warning Center wrote on X. "No tsunami danger presently exists for this area."

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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.

The USGS says Thursday's earthquake was "primarily strike-slip," which is less likely to cause a tsunami because the earth's tectonic plates moved more horizontally than vertically.

The warning had been in effect from Davenport, California, to Douglas/Lane Line Oregon, the National Tsunami Warning Center said.

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

It was reported at 10:44 a.m. local time, according to the National Tsunami Warning Center.

Subsequent earthquakes were reported in the region, including a 5.0 magnitude near Ferndale and a 4.2 magnitude near Petrolia, according to the USGS.

Shake alerts in the USGS's earthquake early warning system were delivered as far north as Lincoln City, Oregon, and as far south as Salinas, California, the agency said.

"System was activated and performed as designed. Still trying to ascertain how much warning people received," the USGS said.

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. As of 3:00 p.m. Thursday, at least 40 aftershocks have been recorded by USGS in Northern California following

The largest aftershock was recorded as a 5.0.

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The San Francisco Zoo announced that guests have been evacuated and animals and staff are moving to higher ground after a Tsunami Warning was issued due to the quake in Humboldt County.

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.

Governor Gavin Newsom says he signed a state of emergency declaration following the earthquake. He says damage assessments are underway.

California State Senator Mike McGuire said on social media that about 10,000 residents are without power in the region and there are reports of homes that have come off their foundation.

Rio Dell Mayor Debra Garnes tells ABC News that there are no injuries reported, but there are cracks in the road and one middle school had a gas leak as a result of the earthquake.

The Ferndale city manager reported minor damage related to roofs.

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."

Regarding aftershocks, there is currently a 5% chance of a magnitude 6 or larger earthquake occurring in the next week, and a 34% chance of a magnitude 5 quake occurring in that time frame, the USGS said.

USGS officials advised people to be prepared for aftershocks in the coming days and weeks.

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

ABC News and the Associated Press contributed to this report.