Workers are assessing damage and have begun to clear up after a 6.0 magnitude quake in California's San Francisco Bay area, the strongest there in 25 years. No-one has been killed but scores of people sought medical care after Sunday's quake, which struck four miles from the town of American Canyon. The quake started fires, cracked roads, caused gas and water leaks and left dozens of buildings uninhabitable. Governor Jerry Brown declared a state of emergency in the affected area. President Barack Obama has also been briefed on the earthquake.