Earlier reports said that three people were killed in a building collapse in the town of Paso Robles on Monday at 11:16am (19:16 GMT). Another 46 people are injured.

The two women, aged 55 and 19, were killed when the town's landmark 19th century clocktower building collapsed, spewing tonnes of debris into the street below, said officials.

The town, in a well-known wine growing area, was believed to be the hardest hit in a quake that overall caused only "modest" damage, said officials. 

The San Luis Obispo County town, about 300km north of Los Angeles, was believed to be the hardest hit in the 6.5 magnitude quake that overall caused only "modest" damage.
   
Police said 46 buildings were damaged, many of them in the
historic downtown area dating to the 1890s. 
 
The quake, one of the largest to strike the seismically active state in recent years, cut electric power to tens of thousands of people but did not appear to cause the massive damage it might have, had it hit a more heavily populated area such as Los Angeles.
   
The US Geological Survey (USGS) said initial damage reports were modest and could be measured in the millions of dollars. By contrast, the Northridge earthquake of 1994 in the Los Angeles area, which measured 6.7, caused more than $40 billion in damage.
   
The epicentre of Monday's quake was located near San Simeon, California, the home of Hearst Castle, the lavish mansion built by newspaper tycoon William Randolph Hearst and one of the major tourist attractions in the state. 

Electricity cut
   
In Paso Robles, the quake shook older buildings along the town's main street, crumbling storefronts and sending hundreds of kilogrammes of bricks and rubble onto cars, said witnesses. A clock tower also collapsed. 

Within one hour of the initial quake 30 aftershocks of magnitude 3.0 or greater were recorded in the region, including one at 4.7.

The quake's depth along the San Simeon fault, part of the state's San Andreas fault system, was measured at eight kilometres.
   
About 40,000 people lost electric power because of the quake but the state's power grid operator said there were no reports of damage to high-voltage lines and no damage to the Diablo Canyon nuclear power generator where the tremblor was felt in the plant's control room.
   
The USGS said the quake would produce hundreds of aftershocks over the next days. 

Within one hour of the initial quake 30 aftershocks of magnitude 3.0 or greater were recorded in the region, including one at 4.7.