The focus in western Indonesia has shifted from a rescue operation into a massive relief effort as teams of workers called off their search for earthquake survivors Monday and instead tried desperately to try to bring food and assistance to the area's most devastated regions.

"The chances of survival while trapped without water and food under the rubble for so long are impossible from now," said Gagah Prakoso, a spokesperson for the Indonesian Search and Rescue Agency. "So we will speed up our search to find bodies and clean up the ruins with bulldozers."

The official death toll from Wednesday's massive earthquake in Sumatra Island stands at more than 600 people, according to the Indonesian government. But authorities say they expect that number to soar into the thousands.

The tremor, which registered a 7.6 on the Richter scale, caused catastrophic damage in 10 districts of the Western Sumatra province, including Padang -- the capital city in which about 900,000 people call home. The city was devastated as scores of tall buildings, schools, mosques, a mall and hotels crumbled under the earthquake's pressure.

About 100,000 public buildings were flattened, 88,000 homes were destroyed and 31 kilometres of road was damaged as a result of the tremor.

The quake also triggered powerful landslides in the hills of Pariaman district, wiping out entire villages. More heavy rain fell Sunday, causing more landslides but no deaths were reported as a result.

Hiroaki Sano, the head of the Japan Disaster Rescue Team, said their efforts have been fruitless.

"We got here quickly but we haven't found any survivors," he told The Associated Press. "The first 100 hours are crucial."

An Indonesian government minister told the media that US$600 million is needed to repair the infrastructure that was completely wiped out during the tremor. Initially, the government said it would need US$400 million but had to raise their estimates after reviewing the scale of devastation.

Relief effort

The UN is "supporting the government now more in the relief side," Ignacio Leon, the head of the UN's humanitarian agency in Indonesia told The Associated Press.

Kathy Mueller, an outreach worker with the Canadian Red Cross, was dispatched to Indonesia after the quake. She told CTV's Canada AM on Monday that the situation needs urgent attention.

"The situation appears to be becoming quite desperate, especially when you get out into the more remote areas," she said in a telephone interview.

Several roads and bridges were destroyed in the remote communities of Pariaman. Landslides blocked roads leading to villages, keeping aid workers out of reach. Crews are working diligently to clear the road of debris but heavy downpours and thick muddy conditions are hampering efforts.

"Clearly the longer this gets into the relief effort, the more it will become a recovery operation," Mueller said. "We need help. The problem isn't so much the earthquake but the aftermath."

She said locals have told her they only have enough food to last them for two days and are in desperate need for clean drinking water.

Mueller also said the Red Cross is seeking donations to help them distribute water, food, mosquito nets and clothes.

In the meantime, authorities are using helicopters to drop aid packages by air and to transport injured civilians to hospitals. Prakoso said two helicopters have conducted six airdrops so far in remote areas, dropping off packages of instant noodles, blankets, milk and dry food.

But officials fear it won't be enough to get people through another several days of strong winds and severe storm weather.

Hari Tirto, a spokesperson for the Meteorological and Geophysics Agency, warned officials that more unstable weather is in the forecast for the region.

"People who live around the hills should remain alert for potential landslides, due to the high intensity of rain," said the agency's spokesman, Hari Tirto.

Nonetheless, officials say they are trying hard to get operations back to normal as quickly as possible.

In Padang, hundreds of young students were sent to school on Monday. Classes were set up in tents that were provided by UNICEF. The charitable organization sent tents and school supplies to schools in three of the 10 affected districts.

The agency is expected to ship another 220 tents by boat from the capital of Jakarta, said Amson Simbolon, a UNICEF education officer. Each tent has rrom for about 50 or 60 students.

"The government has called for classes to resume as soon as possible so they can create some normalcy," he said.