UPDATED 12:57 p.m.
Gov. Jerry Brown has declared a state of emergency for the part of California's wine country hard-hit by a large earthquake.
The governor issued a proclamation directing state agencies to help respond to the 6.0-magnitude quake that struck early Sunday about 6 miles from the city of Napa.
Napa Fire Department Operations Chief John Callanan says the city has exhausted its own resources extinguishing six fires, transporting injured residents, searching homes for anyone who might be trapped and answering calls about gas leaks, water main breaks and downed power lines.
Callanan says three people are reported to be in critical condition, including a young child who was struck by part of a fireplace and airlifted to a specialty hospital for a neurological evaluation.
Inspectors are evaluating damaged buildings, bridges and roads.
Residents in the San Francisco area are bracing for more aftershocks in the wake of an earthquake today, the Weather Channel is reporting.
The aftershocks will likely continue, "probably for weeks," according to a Weather Channel analyst.
The Weather Channel provided the following account:
A preliminary 6.0-magnitude earthquake rocked the San Francisco Bay area early Sunday, according to the U.S. Geological Survey.
The earthquake struck 4 miles northwest of American Canyon, California in Napa County at around 3:20 a.m. local time. The quake was felt over a large portion of northern California, including San Francisco, with the strongest shaking experienced in Napa, Solano and Sonoma Counties.
According to NBC News, the earthquake knocked out power to more than 50,000 people early Sunday. According to the San Francisco Chronicle there were reports of minor damage to westbound Highway 37, but so far there have been no reports of major damage to infrastructure or reports of injuries.