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.

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.

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 activist group International Rivers Network was involved in a campaign in 2001 and 2002 to protest funding for the Zipingpu Dam because of its proximity to a fault line, said Aviva Imhoff, the group’s campaigns director.

Imhoff said the group obtained transcripts of a 2000 internal government meeting in which seismologists warned officials of the dangers of constructing the dam and the potential for it to be damaged in an earthquake, Imhoff said.

Sichuan has other major dam projects, including the massive Three Gorges dam, the world’s largest about 350 miles east of the epicenter. The information office of State Council Three Gorges Construction Committee said earlier this week that there was no damage to the dam.

The official death toll rose Wednesday to 14,866, and in Sichuan province another 25,788 people were buried and 1,405 were missing, provincial vice governor Li Chengyun said, according to Xinhua.

An already massive military operation gathered pace with close to 100,000 soldiers and police mobilized. After two days of rain that prevented relief flights, People’s Liberation Army helicopters flew 90 sorties to the epicenter in Wenchuan county and other areas to drop food, medicine and tents and ferry out 156 injured people, Xinhua reported.

Aerial TV footage showed rows of small buildings flattened in Yingxiu in Wenchuan county, where rescuers who hiked in said they found only 2,300 survivors in the town of about 10,000, with another 1,000 badly hurt, Xinhua reported.

The scale of the devastation is raising questions about the quality of China’s recent construction boom. Some builders cut corners, especially in outlying areas largely populated by the very young and very old.

With help slow in arriving, some fled Yingxiu on foot, carrying injured family members in wheelbarrows. One woman “carried a dead infant wrapped in white clothes as if the baby was alive,” the agency said, citing a reporter who hiked to the area with military rescue teams.

Ships from a temporary dock built at a reservoir sailed to Yingxiu, but blocked roads meant heavy digging equipment could not be brought in. Most rescuers were using their hands, Xinhua reported.

The death toll from the quake was expected to rise when rescuers reach other towns in Wenchuan county that are still cut off.

“The Communist Party Central Committee has not forgotten this place,” Premier Wen Jiabao said after flying by helicopter to Wenchuan.

President Hu Jintao presided at an emergency meeting of the party’s powerful Politburo, urging the military, police and others to redouble rescue and relief efforts.

Unlike previous natural disasters in China, official media have reported prominently on the quake, and state TV replaced regular programming with 24-hour coverage.

Scenes of destruction and death have been shown with a prominent focus on Wen, the normally staid leadership’s most popular member who has been shown crawling into collapsed buildings to urge survivors to hang on with impassioned pleas and reassuring children who lost parents.

Amid the tragedy, onlookers erupted into cheers and applause when a 34-year-old woman who was eight months pregnant was rescued after spending 50 hours under debris in the Dujiangyan area.

“It’s a miracle brought about by us all working together,” said Sun Guoli, fire chief of the nearby provincial capital, Chengdu, who supervised the rescue.

But the rescuers called off the search for four others still trapped in the collapsed building, leaving only a smaller crew of dogs to sniff for signs of life.

In Hanwang, the smell of incense hung over a crowd of sobbing relatives who walked among some 60 bodies wrapped in plastic, some covered with tributes of branches or flowers. Nearby, rescuers carried more bodies out of a makeshift morgue at the Dongqi sports arena.

People from the town and surrounding areas packed into blue tents provided by relief officials. Though the mostly older buildings in the town collapsed, a newer Western-style clock tower still stood, its hands stopped at 2:27 — the time the quake hit.

The Mianzhu No. 3 Hospital was obliterated, and the seven-story main Hanwang Hospital collapsed. Surviving medical staff set up the triage center in the tire factory driveway, but could only provide basic care.

Emergency vehicle sirens sounded every few minutes. An ambulance drove in, delivering a man pulled from the rubble and covered in dust.

“There will be a lot more people. So many still haven’t been found,” said Zhao, the nurse.

Farther north in An Xian, disaster victims huddled by the road in front of their destroyed homes under a makeshift wood-and-plastic shelter to protect them from the rain. Government buses have brought some survivors from devastated areas, but 38-year-old farmer Li Zizhong said he had not heard from his relatives there yet.

“Who knows what happened to them?” Li said. “All we need is a little something to eat. I’m just happy to be alive.”

Disorienting episodes added to the struggle for survival in much of the disaster zone. The Mianyang city government ordered its 700,000 residents to evacuate all buildings between 4 p.m. and 6 p.m. because an aftershock was predicted.

In Chengdu, water to some parts of the city was cut for repairs, touching off a rumor that the supply was contaminated. People began hoarding water, and water pressure citywide dropped before a senior official went on TV to deny anything was wrong.

The disaster also cast a pall over the Olympic torch relay that resumed Wednesday in eastern Fujian province away from the quake’s reach, pausing for a minute of silence before the event building up to the Beijing Summer Games in August. Runners asked for donations to earthquake victims, Xinhua said.