Hanwang, China ? Soldiers rushed to shore up a dam cracked by this week’s powerful earthquake, and rescuers came by helicopter and ship Wednesday into the isolated epicenter but still were forced to dig for survivors with their bare hands.

Today, the Defense Ministry ordered 100 more helicopters into areas of Sichuan, underscoring worries that deaths will skyrocket unless help for the needy arrives soon, state media said.

Nearly 26,000 people remained buried in collapsed buildings from Monday’s magnitude 7.9 earthquake, and the death toll of almost 15,000 was expected to climb as relief operations spread into the mountains of Sichuan province. The quake triggered landslides that blocked roads to hardest-hit areas.

Even as the rescue effort seemed to gather momentum – speeded by clearing weather after two days of rain – caring for tens of thousands of people made homeless across the disaster zone have stretched thin the government’s resources. State media reported that 10 million people have been directly affected by the quake – a figure equal to the populations of New York City and Dallas combined.

Homeless victims begged for aid on roadsides, and people settled in for a third night in a growing sprawl of refugee camps littered with garbage. In Hanwang, a town in one of the hardest-hit counties, survivors stood hoping for handouts from cars, jostling with each other to reach to one vehicle where a passenger passed bottled water out the window.

“I’m numb,” said Zhao Xiaoli, a 25-year-old nurse working at a makeshift triage center in tire factory driveway. “The first day, hundreds of kids died when a school collapsed. The rest who came in had serious injuries. There was so little we could do for them.”

Damage to the two-year-old Zipingpu Dam threatened downstream communities still digging out from the quake. Some 2,000 soldiers were sent to the dam, the official Xinhua News Agency said. Four-inch cracks scarred the top of the dam, and landslides had poured down the surrounding hills, the business news magazine Caijing said on its Web site in a report from the scene.

Although the government pronounced the dam safe late Tuesday after an inspection, Caijing said its waters were being emptied to relieve pressure. The Ministry of Water Resources issued a notice to check reservoirs nationwide, while the economic planning agency said nearly 400 dams, most of them small, were damaged by the quake.

Hundreds of rivers snake through the mountainous Tibetan plateau before descending into the fertile Sichuan basin where they provide critical irrigation.

The massive Three Gorges dam, the world’s largest, is about 350 miles east of the epicenter, wasn’t damaged, officials said.