Rescue workers called off the search Monday for life under the rubble left by a massive earthquake, focusing instead on bringing aid to survivors in the towns and hills of western Indonesia, despite being hampered by torrential rains.

"The chances of survival while trapped without water and food under the rubble for so long are impossible from now," said Gagah Prakoso, a spokesman 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 death toll from Wednesday's 7.6-magnitude temblor in Sumatra island is expected to be in the thousands once the missing people are declared dead. The U.N. has said 1,100 people died, while the government puts the toll at 603.

Ignacio Leon, the head of the U.N.'s humanitarian agency in Indonesia, told the AP that the focus has now shifted away from finding survivors and "we are supporting the government now more in the relief side."

View photos from the powerful earthquake

The undersea quake devastated 10 districts in the Western Sumatra province including the capital, Padang, a city of 900,000 people where scores of tall buildings, including hotels, a mall, mosques and schools came down crashing. In addition, the quake triggered huge landslides in the hills of Pariaman district where entire villages were wiped out.

Hiroaki Sano, head of the Japan Disaster Rescue Team, told the AP that international search and rescue teams were winding up operations and preparing to go back home.

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

Government minister Aburizal Bakrie told reporters that $600 million was needed to repair infrastructure. It had initially said $400 million was needed, but raised the estimate after the scale of the disaster became clear.

Little aid has reached the remote communities in Pariaman as many roads and bridges were destroyed. Landslides also blocked many of the roads leading to villages and an AP crew saw aid workers scrambling to clear the road of dirt, boulders and trees.

One road ended at Kampung Dalam village. The rest of the way had caved in, forcing rescue teams from South Korea, France and Germany to camp there. Villages further up the road were now accessible only by foot.

Heavy rain since Sunday night triggered a landslide on Monday but no casualties were reported, according to Prakoso, the rescue agency spokesman. Still, most aid teams were forced to stay put in Padang because of the rain.

He said the downpour and thick wet mud is making it "difficult for us to reach areas in need of aid."

Authorities are using helicopters to airdrop aid and bring the wounded to hospitals, he said. Two helicopters have conducted six airdrops in isolated areas so far, delivering instant noodles, blankets, milk and dry food, he said.

The Meteorological and Geophysics Agency warned the region could see strong winds and storms for the next two days.

"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.

It was unclear precisely how many people were without shelter Monday, but more than 88,000 houses and 285 schools were flattened in 10 affected districts, according to the U.N. and Indonesia's Disaster Management Agency.

Another 100,000 public buildings and 20 miles (31 kilometers) of road were damaged.

In Padang, hundreds of children went back to class Monday in schools set up in tents as authorities tried to restore normalcy. UNICEF provided tents and basic supplies for schools in three of 10 affected districts.

The resumption of classes was largely symbolic, giving just a few hundred children an opportunity to meet with teachers and receive counseling to process the trauma of recent days, including the deaths of relatives and being made homeless.

"The government has called for classes to resume as soon as possible so they can create some normalcy," said Amson Simbolon, a UNICEF education officer, as math classes began for around 300 students at one badly damaged school in Padang.

The agency has provided 15 tents, each with room for 50 to 60 children, and is shipping another 220 by boat from the capital of Jakarta, he said.