Two people were hurt and a bridge was damaged by a violent 6.4-magnitude earthquake that occurred off the coast of northern California on Tuesday. Thousands of homes and businesses also lost power.

According to the U.S. Geological Survey (USGS), the earthquake occurred around 2:34 a.m. local time (10:34 GMT) and was about 10 miles (16.1 km) deep. It happened near Ferndale, California, which has a population of around 15,000 and is situated 7.4 miles (12 km) to the west-southwest of Ferndale. Ferndale is in Humboldt County, 261 miles (420 km) north of San Francisco and just south of Eureka.

The earthquake caused numerous gas leaks, downed powerlines and at least one structure fire in Ferndale, local media reported.

Two people were injured in Humboldt County, where widespread damage to roads and homes was reported, the sheriff’s office said on its website. It did not give details on the extent or circumstances of the injuries. It is unclear if the earthquake caused any deaths.

“Be prepared for aftershocks. Check gas and water lines for damages or leaks. Exercise caution if traveling,” the office said on Twitter.

Local media reported that the California highway patrol was responding to reports of cracks in the Ferndale bridge over the Eel River in and out of Ferndale.

Highway 101 and Highway 299 remained open through Humboldt County, State Senator Mike McGuire said on Twitter, noting that transportation officials were assessing state highway infrastructure.

“That earthquake was insane,” said Twitter user Jimmy Eller, who said he lived in Humboldt County. “A good 15-20 seconds of shaking.”

The earthquake caused strong shaking and likely produced light to moderate damage, according to the USGS, which uses a seismometer to measure the time, location and magnitude of a tremor. An earthquake’s intensity depends on its distance from a fault, its direction and the local geology.

About five earthquakes of magnitudes between 6.0 and 7.0 happened each year in California and Nevada, according to recent data, the Los Angeles Times reported.

More than 3,500 people reported to the USGS that they felt the earthquake and the more than a dozen aftershocks reported in the aftermath, the service said online.

Caroline Titus, the editor and publisher of The Ferndale Enterprise, posted video on Twitter of toppled furniture and household items scattered on the floor.

“Sorry for dark video. Power still out,” Titus tweeted from Ferndale.

More than 72,000 homes and businesses were without power in Ferndale and surrounding Humboldt County, according to the electric grid tracking website Poweroutageus.com.

The California Independent System Operator, which oversees much of the state’s electrical grid, issued a transmission emergency notice for the area following the earthquake.

There was no risk of a tsunami, the U.S. tsunami warning system said.