Bay Area residents awake in the early hours of Sunday morning felt waves of a magnitude 6.1 earthquake, whose epicenter was approximately nine miles south of Napa and 40 miles north of Berkeley.

Gov. Jerry Brown declared a state of emergency in the wake of the earthquake, which struck 44 seconds after 3:20 a.m., according to the U.S. Geological Survey. It’s the largest earthquake in the Bay Area since the magnitude 6.9 Loma Prieta earthquake in 1989.

At 5:43 a.m., Napa city authorities reported that buildings in their downtown area suffered extensive damage, including a historic courthouse and library. At 6:30 a.m., officials reported that at least 87 patients were being treated at Queen of the Valley Medical Center, three of which were classified as major injuries. In north Napa, four mobile homes were destroyed and two were on fire. Two other fires in residential areas were extinguished by local fire crews.

Napa authorities also reported that crews were responding to at least 50 gas line breaks. There were approximately 30 water main leaks, although water remained safe to drink for Napa residents. More than 69,000 residents across California are without power, according to the governor’s office.

In Napa, the American Red Cross set up a shelter for displaced individuals at Napa High School’s gym, which later moved to a nearby church. The county’s emergency operations center was activated and is working to assess the situation. Ten engines from Cal Fire, the state’s Department of Forestry and Fire Protection, assisted with the earthquake and aftershock calls.

At 10:18 a.m., California Highway Patrol reported that all roads in its jurisdiction were open and accessible to the public, but the agency urged people to avoid entering Napa unless they have urgent business there.

According to the Geological Survey, the probability of strong aftershocks in the next seven days is 45 percent. There is a 5 to 10 percent chance that an earthquake of equal or larger magnitude will hit in the next week.

Check back for updates.

Kimberly Veklerov is a news editor. Contact her at kveklerov@dailycal.org and follow her on Twitter @KVeklerov.