MANJIL, IRAN, JUNE 24 -- Cranes, bulldozers and dump trucks have arrived in this once-picturesque town beside a blue-gray reservoir, but today hardly anyone was using them to search for survivors in the rubble that was once Manjil, where an estimated 5,000 people died Thursday in an earthquake that flattened much of northwestern Iran.

There are believed to be no survivors beneath the town's sprawl of collapsed houses and shops, relief workers said. A French team came Saturday with rescue dogs and combed the entire city, finding no signs of life. So now the mechanical shovels have been dispatched to a dirt pit by the reservoir, where they dig long trenches for the dead.

Mourners marched in ragged lines to and from the makeshift cemetery. Women sat, enveloped in black chadors, and wept with their children on fresh graves. Some families made small headstones from fragments of their decimated homes. Gravediggers outfitted in orange jumpsuits, with handkerchiefs tied over their faces, swung their picks among the mourners.

Some in this stricken town are too dazed to do more than wander aimlessly among the tent camps where many of the survivors and refugees now live.

"This is God's work," said Gholam Atedadi, whose wife and three children died when their house collapsed. Atedadi escaped with scratches and a head wound, then spent two days pulling his family from the wreckage and burying them. "I don't worry about this other relief work -- this belongs to God. In time, some future will come."

The images in Manjil are mirrored in villages and towns around the northwest, where Iran's government estimates that more than 40,000 people died in Thursday's earthquake, which measured 7.3 on the Richter scale and was the worst in Iran's history.

{Iran has told the United Nations that the death toll could rise to 50,000, M'Hamed Essaafi, U.N. undersecretary general in charge of the U.N. relief effort for the quake, said in Geneva. Essaafi, quoted by the Reuter news agency, said well over 100,000 people are estimated to have been injured and 500,000 are believed to be homeless.}

A sizable aftershock today hampered the Iranian government's massive relief efforts in the region. The quake, which according to the offical Iranian news agency IRNA measured 5.7, rumbled through the afflicted northwest at 1:16 p.m. (5:46 a.m. EDT).

There were no official estimates on how many people were killed or injured by the aftershock. Dozens of ambulances raced toward Tehran from the northwest this afternoon carrying wounded. But there were few signs that the aftershock caused widespread deaths or major new damage, largely because the towns and villages where the shock was strongest already were virtually flattened and residents have moved out of the remaining buildings and into tents.

A smaller tremor, which IRNA said measured 4.9, rattled southern Iran today, but there was no loss of life or property reported.

On the roads between Manjil and Tehran, boulders broke free from a cliff face following the aftershock and crashed onto the main road to Tehran, temporarily closing the route. But bulldozers cleared the debris within hours, and by evening trucks were rolling again.

The aftershocks have made nearly all of the overland routes through the northwest precarious, and fresh landslides block some mountain roads. The faces of barren hillsides in the earthquake region continue to crumble, sometimes sending house-size boulders tumbling toward highways and villages below.

Army and refugee camps in Manjil and other towns on or near the main road from Tehran were well supplied with food, clothing and tents. Residents of the area sometimes complained of inefficiency in distribution and of high-handedness by the Revolutionary Guards, the Islamic fundamentalist fighting force established by hard-line mullahs after the 1979 revolution led by Ayatollah Ruhollah Khomeini. But, they said, there was no shortage of basic necessities.

Refugees and relief workers said fewer supplies had reached scores of isolated mountain villages now accessible only by air.

Foreign relief workers, primarily from Europe and Japan, have begun to fan out across the northwest, but for the most part the Iranians are handling the massive supply and relief effort by themselves. Donations of clothes and food from Iran's major cities have begun to arrive in the northwest, shipped in army dump trucks.

In Manjil and other towns nearby, the army has played a major role in distribution. Most of the soldiers involved are veterans of Iran's bloody nine-year war with Iraq during the 1980s, but they say the destruction caused by the earthquake here is worse than what they saw in battle.

"This is much, much worse than the Iraq war," said Capt. Haj Ali, who supervised a relief distribution center in Laushan, and bears several scars from gunshot wounds. "I saw many things in the war, but I never saw anything like this."

The able-bodied men of Manjil and nearby towns occupy themselves with burials, relief work and small acts of reconstruction -- hoisting a ladder to repair a damaged power line, hauling sacks of bread from the transit point where supplies from Tehran arrive, and hacking at 10-foot heaps of rubble with shovels and picks.

In a refugee camp near Laushan, two survivors argued about whether it was possible to reconstruct their homes and villages. "The town is finished," said Ghorbanali Pirouz, 25, a factory worker. "We cannot make these houses again. There are too many. It is too hard."

"I have seen that the rocks can be moved," said Ali Mooradi, who dug through the rubble of his sister's home to pull out the bodies of her and four other relatives. "If we can dig, we can build."

There were long lines today at relief centers in Tehran, where residents donated clothing, food and cash. Hospitals have reported heavy donations of blood since Thursday.

Iran's large extended families provide one way for survivors to find assistance -- and also to measure their loss. In the refugee camps, survivors talk of 30 or 40 dead in their families, including cousins and relatives by marriage.

The local mullahs who survived the quake came to the cemetery to lead prayers and offer condolences. Young Revolutionary Guards controlled traffic and chased off loiterers at food distribution sites. But in general, the Islamic fundamentalism for which Iran is primarily known in the West does not appear to have influenced greatly the management of relief efforts or the emotional responses of survivors.

Dozens of survivors and refugees interviewed in Manjil and elsewhere during the past two days spoke rarely of Islam while describing their reactions to the disaster. Instead, they spoke mainly of family, coordination of relief and other practical matters.

"These natural disasters can strike anywhere," said Zachalor Khalov, 22, an unemployed resident of Manjil. "What I don't understand is why there is no machine to say when and where an earthquake will strike."

A Tehran newspaper that represents the views of radical fundamentalist mullahs lashed out in an editorial at the United States, saying that U.S. "plots" against Iran have prevented the country from developing seismic technology that might have predicted Thursday's earthquake or lessened its destruction.

"Our people, even under the rubble, chant 'death to America' and pray to God to cut off the hands of the United States, . . . even those hands stretched out to help," the newspaper Jomhuri Islami said, according to the official news agency.

In general, however, the government of President Ali Akbar Hashemi Rafsanjani has been receptive to offers of aid from its Western adversaries since the quake struck, and the country has temporarily opened its borders to journalists and television cameramen seeking to cover the disaster.