Two women were crushed Monday when the roof and second floor of the landmark 19th century clock tower building collapsed, officials said. The women were identified as Jennifer Myrick, 19, and Marilyn Zafuto, 55.

A three-hour search of the wreckage of the building by a Ventura County urban rescue team with a dog produced no results.

"We searched any possible place that victims could be. We're very comfortable and confident that nobody else is inside," said Ventura County Fire Department Battalion Chief Scott Hall.

Police cordoned off a five-square-block area of historic Paso Robles and planned to spend the night patrolling to prevent looting, said police spokesman Sgt. Bob Adams.

Called the San Simeon earthquake after the coastal town nearest its epicenter, the temblor struck at 11:16 a.m. PST on Monday, hitting hardest in this town known for its sulfur springs and mud baths.

Power was cut to some 75,000 homes and businesses and the quake shook the historic Hearst Castle, a major California tourist attraction.

At least 82 commercial buildings in town were damaged, many of them in the historic downtown area dating to the 1890s, said Doug Monn, the town's top building official.