Fire officials said about 24 homes in the scenic beach town north of San Diego could be at risk if the slippage continues. But San Diego city attorney Michael Aguirre told reporters no-one was in immediate danger.

""We do not believe there is an immediate threat to residents. There does not appear to be any additional cracking at this point," Aguirre said. "This is a dynamic situation so we are not able to say for certain it won't become more of a problem."

One home in the mountainside area of million dollar plus properties slipped off its foundations and its roof caved in. A 50 to 60 yard (metre) sinkhole scarred the road where the collapse occurred.

One homeowner said the road was blocked by about 25 feet (7.5 metres) of dirt.

As the land shifted, resident Ross Clark wrote on a newsblog on the San Diego Union Tribune newspaper Web site that he was "looking at the mountain going into my pool and the neighbor's house."

"I heard the fence starting to crack. I heard a tree coming down. We grabbed the dogs and ran," he said, adding that he and his wife returned a short time later.

The area has a history of land slippages going back to the 1960s. The most recent street cracks and waterline breaks were noted in July and August, and engineers had warned residents this week that the hillside was again unstable and was threatening as many as eight houses.