(Reuters) - A strong 6.4-magnitude earthquake that struck off the coast of northern California on Tuesday injured two people, damaged a bridge and several roads and left thousands of homes and businesses without power.
The earthquake struck at 2:34 a.m. local time (1034 GMT) and was about 10 miles (16.1 km) deep, the U.S. Geological Survey (USGS) said. It struck about 7.4 miles (12 km) west-southwest of Ferndale, California, a Humboldt County town home to about 1,400 people and located 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. One of those injured was a juvenile with a head injury and the other an older person with a broken hip, according to local media citing the sheriff's office.
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.
Police have closed the Ferndale bridge over the Eel River in and out of Ferndale because of four large cracks in the bridge and the roadway is at risk of sliding, the California Highway Patrol said.
Officials have closed at least four roads in Humboldt County because of large cracks, some with the smell of natural gas in the area from a possible gas line rupture, the highway patrol said. One road section was reportedly sinking, the patrol said.
Highway 101 and Highway 299 remained open through Humboldt County, State Senator Mike McGuire said on Twitter.
J.B. Mathers, a Eureka, California, resident told CBS News his home "shook and shook and shook."
"Anything that was on the walls broke off the walls -- fish tank and all," Mathers also said. "It's still pretty dark here. We can't assess the damage."
The earthquake 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.
Some 72,000 homes and businesses were without power in Ferndale and surrounding Humboldt County, according to the electric grid tracking website Poweroutageus.com.
PG&E crews were out assessing the utility's gas and electric system for any damage and hazards, company spokesperson Karly Hernandez wrote in an email to Reuters.
"Our assessment could take several days," Hernandez wrote. "Customers are urged to use extreme caution around heavily damaged buildings and be prepared for further aftershocks that can create more destruction and hazards."
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.