Crews dug away at masses of mud, boulders and debris with earth-moving machines and shovels on Saturday in a California town ravaged by mudslides which have killed at least 18 people.

The army of searchers and recovery workers in Montecito trying to find seven people still missing swelled to more than 2,000 five days after a powerful storm swept in from the Pacific.

It dumped a deluge on mountain slopes above the coastal enclave that were burned bare by a huge wildfire in December.

The backbreaking work went on under the sunny skies that have made the stretch of Santa Barbara County coast about 90 miles north-west of Los Angeles a haven for the wealthy.

“We have to do whatever it takes,” said Captain Tom Henzgen, leader of a team from the Los Angeles Fire Department.

Long-range forecasts gave the crews about a week before the next chance of rain – and potential new mudslides – although the precipitation expected next Friday was expected to be disorganised and light. Another system was possible two days later.

Much of the community of about 9,000 remained under mandatory evacuation orders as crews both removed debris and worked to restore water, sanitation and power.

All warnings and orders for neighbouring Summerland and Carpinteria were lifted.

Tanker trucks sucked muddy water from flooded sections of US 101, the only direct major artery between Los Angeles and the Santa Barbara region.

The California Department of Transportation abandoned an estimate of reopening the highway on Monday and said it was not known when the closure would be lifted.

Amtrak, which began restoring rail service two days after the flood, was adding cars to trains because of heavy demand.

Two boat companies that normally take tourists out to Channel Islands National Park and on whale-watching excursions were ferrying people between the Ventura and Santa Barbara harbours.

On land, local, state and federal agencies were conducting simultaneous recovery efforts, the Santa Barbara County Public Works Department said.

That included clearing roads, drainage channels and debris basins that are intended to catch mudflows.

Emergency permits were obtained to dump up to 229,365 cubic metres of sediment into the surf line on beaches in Goleta and Carpinteria.

The department said the sediment would only consist of wet or dry dirt or mud without rocks, debris or vegetation, and inspectors would refuse any truckload containing unpermitted materials.

Santa Barbara County said emergency permits do not require testing of the material for hazards but that public health authorities were testing the ocean waters.

Down the coast in Ventura County, environmental health officials warned that storm run-off can carry disease-causing bacteria and advised the public to avoid contact with ocean water until sampling results can be reviewed next week.

In the disaster impact zone, searchers used chain saws and rakes to remove logs and sift through the remnants of what was left of multimillion-dollar homes.

Crews with backhoes and jackhammers pulverised enormous boulders that were left when the torrents stopped.

Orange markings left on doors indicated which homes had already been searched.