LOS ANGELES (AP) — A strong earthquake rattled a large swath of Southern California and parts of Nevada on Thursday, rattling nerves on the July 4th holiday and causing some damage in a town near the epicenter amid a swarm of ongoing aftershocks.

The 6.4 magnitude quake struck at 10:33 a.m. in the Mojave Desert, about 150 miles (240 kilometers) northeast of Los Angeles, near the town of Ridgecrest, California. It is the strongest quake to hit the region in 20 years.

Peggy Breeden, the mayor of Ridgecrest, a town of 28,000 people, said firefighters were working to put out five fires, at least one of them at a home, but that she didn’t know if any injuries had been reported.

Utility workers were assessing broken gas lines and turning off gas where necessary, Breeden told CNN.

She said the local senior center was holding a July 4th event when the quake hit and everyone made it out shaken up but without injuries, she said.

“Oh, my goodness, there’s another one (quake) right now,” Breeden said on live television as an aftershock struck.

President Donald Trump said he was fully briefed on the earthquake and that it “all seems to be very much under control!”

A series of aftershocks included a 4.5 magnitude temblor, according to the United States Geological Survey.

“It almost gave me a heart attack,” said Cora Burke, a waitress at Midway Cafe in Ridgecrest, of the big jolt. “It’s just a rolling feeling inside the building, inside the cafe and all of a sudden everything started falling off the shelf, glasses, the refrigerator and everything in the small refrigerator fell over.”

Video posted online of a liquor store in Ridgecrest showed the aisles filled with broken wine and liquor bottles, knocked down boxes and other groceries strewn on the floor. Flames were seen shooting out of one home in the community.

Lucy Jones, a seismologist with the California Institute of Technology’s seismology lab, said the earthquake was the strongest since a 7.1 quake struck in the area on October 16, 1999.

Jones said that the 6.4 quake centered near the town of Ridgecrest was preceded by a magnitude 4.2 temblor about a half hour earlier.

She said vigorous aftershocks were occurring and that she wouldn’t be surprised if a magnitude 5 quake hit but that they were striking in a remote area, sparsely populated area. “This is an isolated enough location that that’s going to greatly reduce the damage,” she said.

People from Las Vegas to the Pacific Coast reported feeling a rolling motion and took to social media to report it.

Local emergency agencies also took to social media to ask people to only call 911 for emergencies.

“We are very much aware of the significant earthquake that just occurred in Southern California. Please DO NOT call 9-1-1 unless there are injuries or other dangerous conditions. Don’t call for questions please,” the LAPD said in a statement published on Twitter.

There were no reports of serious damage or injuries in Los Angeles, the department said.

Ashleigh Chandler, a helicopter rescue EMT at Fort Irwin, California, said the quake happened as she was getting ready for a July 4th party.

“I was just in the living room getting everything ready, we start to feel the shaking, so then I look up and then the wine bottles start rattling and I thought, ‘They’re going to fall.’

“My stepson was in the house and my dog, so we just got everyone outside and then it ended. It was like 15, 20 seconds, maybe. It was pretty good shaking, so I’m out of breath.”

“Everyone’s OK.”

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Rodriguez reported from San Francisco. Associated Press writer Rachel Lerman in San Francisco and AP Radio reporter Shelly Adler in Washington, D.C., contributed.

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The quote in the story from Ashleigh Chandler has been corrected to say stepson, not sister.