Authorities said a magnitude 6 earthquake jolted both sides of the California-Nevada border, tossed boulders onto a major highway, and was felt as far away as Las Vegas and even San Francisco, with days of aftershocks expected.

The quake struck shortly before 4 p.m. Thursday near Walker, a rural community of a few hundred people in the eastern Sierra Nevada. Authorities reported no major damage or injuries.

According to the US Geological Survey, it was followed by dozens of aftershocks, including at least a half-dozen of magnitude 4 or higher. There were no reports of serious damage or injuries at the time.

At 3:49 p.m., the earthquake struck a region about 250 miles (402 kilometers) east of San Francisco and south of Lake Tahoe. Its epicenter was 4 miles (6.5 km) west-southwest of Walker, a town of less than 900 people in California. According to the USGS, it was followed by a dozen aftershocks, at least one of which had a magnitude of 4.6“The ground was trembling a lot, and then everything started falling,” said Carolina Estrada, manager at Walker Coffee Company. Syrup bottles shattered, dishes fell to the ground, and the shop’s roof caved in slightly.

She estimated that the shaking lasted 30 seconds or more.

“We fled the building,” Estrada said. However, the shaking persisted, and “boulders the size of cars” fell onto nearby US 395, she said.

The California Highway Patrol reported that cars were hit by rocks, but no one was hurt.

Authorities said that at one point, rockslides closed about 40 miles (64 km) of the interstate, a major route through the northern Sierra Nevada. According to the California Department of Transportation, portions of the interstate were later reopened, but crews remained on the scene in case of aftershocks.

Reno City Hall in Nevada has been evacuated, according to Mayor Hillary Schieve.

“It shook a lot,” Schieve said.

According to Graham Kent, director of the University of Nevada, Reno’s seismological lab, “this would be the largest one in almost two and a half decades.”

The earthquake, which had a depth of 6 miles, was felt in communities all around Lake Tahoe and as far south as Fresno, California (9.8 km). According to seismologist Lucy Jones, the quake was “a classic normal faulting earthquake for eastern California,” and aftershocks were common in the area.

More than 30 aftershocks were reported in the first two hours, with at least five of magnitude 4.0 or higher, according to the USGS.

“People in the area should expect aftershocks for days following an earthquake of this magnitude,” said Jason Ballman of the University of Southern California’s Southern California Earthquake Center. “There has already been a fairly vigorous aftershock sequence.”

Because much of the shaking was felt in remote areas, Ballman warned that reports of damage or injury might not be available for several days. According to preliminary reports, two earthquakes struck 25 seconds apart but 100 miles apart. According to the Sacramento Bee, the US Geological Survey revised the shaking and removed the report of a magnitude 4.8 quake in Farmington, about five miles (8 kilometers) southeast of Stockton.

“While there have been no preliminary reports of damage or injuries, this is a rapidly evolving situation, and more information will be released in the coming hours.” The California Office of Emergency Services issued a tweet. “We are collaborating closely with local officials to ensure that they have the resources and support they need to respond quickly to these earthquakes.”