The State Department identified two Americans who died in Nepal’s devastating earthquake, and reported two more dead Monday, as the death toll rose past 4,000 and survivors dug through the rubble of their villages seeking shelter and food.

Saturday's 7.8 magnitude earthquake triggered an avalanche that buried part of the Mount Everest base camp, killing 18 people, including foreign climbers preparing to make their summit attempts at the world’s tallest peak.

At least four Americans died in the quake, all at the Mount Everest base camp the State Department said Monday. State Department spokesman Jeff Rathke identified two of the American victims as Ely Taplin and Vinh B. Truong.

Two others haven't been named yet, either because consular officials haven't confirmed their identities or next of kin haven't been notified.

“We express our deepest sympathies to the families and loved ones of those who died,” Rathke told reporters. He said the State Department was fielding hundreds of calls from Americans asking for assistance and concerned about the safety of loved ones in Nepal.

More On This...

“We are supplementing our embassy staff to better respond to U.S. citizens and liaison with the Nepal government,” Rathke said.   

In addition to the more than 4,000 dead in Nepal, another 61 people were killed in neighboring India, and China reported that 20 people had died in Tibet.

Meanwhile, tens of thousands of families slept outdoors for a second night, fearful of aftershocks that have not ceased. Camped in parks, open squares and a golf course, they cuddled children or pets against chilly Himalayan nighttime temperatures.

"It's overwhelming. It's too much to think about," said 55-year-old Bijay Nakarmi, mourning his parents, whose bodies were recovered from the rubble of what once was a three-story building.

Reports received so far by the government and aid groups suggest that many communities perched on mountainsides are devastated or struggling to cope as they search for lost loved ones, sort through rubble for their belongings, and try to find food and shelter for their families.

Lila Mani Poudyal, the government's chief secretary and the rescue coordinator, said the recovery was slow because many workers -- water tanker drivers, electricity company employees and laborers needed to clear debris -- "are all gone to their families and staying with them, refusing to work."

World Vision aid worker Matt Darvas reached Nepal's Gorkha district -- the epicenter of Saturday's powerful quake -- early Monday afternoon. He said almost no aid had reached there ahead of him.

"It does not seem aid is reaching here very quickly," Darvas told the Associated Press by phone from Nepal.

Udav Prashad Timalsina, the top official for the Gorkha district, said he was in desperate need of help. "There are people who are not getting food and shelter. I've had reports of villages where 70 percent of the houses have been destroyed," Timalsina he said.

He said 223 people had been confirmed dead in the district, but he presumed "the number would go up because there are thousands who are injured." Landslides and other destruction delayed attempts to reach the district earlier, but Gorkha is feared to have extensive damage.

"Villages like this are routinely affected by landslides, and it's not uncommon for entire villages of 200, 300, up to 1,000 people to be completely buried by rock falls," Darvas said. "It will likely be helicopter access only."

"Further north from here the reports are very disturbing," Darvas reported. He says up to 75 percent of the buildings in Singla may have collapsed and the village, a two-day walk away, has been out of contact since Saturday night.

Local officials lost contact with military and police who set out for Singla, and Darvas says helicopters have had to turn back because of clouds. He says a few SUVs with foreign tourists bringing basic aid supplies had begun to reach Gorkha by early evening.

Jagdish Pokhrel, the clearly exhausted army spokesman, said nearly the entire 100,000-soldier army was involved in rescue operations. "We have 90 percent of the army out there working on search and rescue," he said. "We are focusing our efforts on that, on saving lives."

Kathmandu district chief administrator Ek Narayan Aryal said tents and water were being handed out Monday at 10 locations in Kathmandu, but that aftershocks were leaving everyone jittery.

"There have been nearly 100 earthquakes and aftershocks, which is making rescue work difficult. Even the rescuers are scared and running because of them," he said.

The capital city is largely a collection of small, poorly constructed brick apartment buildings. But outside of the oldest neighborhoods, many in Kathmandu were surprised by how few modern structures collapsed in the quake.

Emergency aid flights are landing in Nepal, with relief workers from several different countries who will try to locate and rescue victims. But the dire conditions and communication obstacles are adding to the chaos at the small airport in Nepal's capital of Kathmandu, where there were major backups on the tarmac.

India's defense ministry says four Indian Air Force planes carrying communication gear, aid supplies and rescue personnel were forced to return to New Delhi today because of airport congestion.

The quake will probably put a huge strain on the resources of this impoverished country best known for Everest, the highest mountain in the world. The economy of Nepal, a nation of 27.8 million people, relies heavily on tourism, principally trekking and Himalayan mountain climbing.

The first nations to respond were Nepal's neighbors -- India, China and Pakistan. Other countries sending support Sunday included the United States, Canada, the United Arab Emirates, Britain, Germany, France, Poland, Italy, Israel and Singapore.

An American military plane left Delaware's Dover Air Force Base for Nepal, carrying 70 people, including a disaster-assistance response team and an urban search-and-rescue team, and 45 tons of cargo, the Pentagon said.

The earthquake was the worst to hit the South Asian nation in more than 80 years. It destroyed swaths of the oldest neighborhoods of Kathmandu and was strong enough to be felt across parts of India, Bangladesh, China's region of Tibet and Pakistan.

Nepal's worst recorded earthquake in 1934 measured 8.0 and all but destroyed the cities of Kathmandu, Bhaktapur and Patan.

The Associated Press contributed to this report.