Updated

International relief officials are making a desperate appeal for cash for quake-ravaged Pakistan ahead of a key donor's conference, saying Tuesday that only weeks remain to reach hundreds of thousands of helpless villagers before winter cuts off their remote Himalayan communities.

With temperatures already dipping below freezing, the world has still come up with just a fraction of the tents needed to house the suffering.

Meanwhile, a U.S. Army MASH (search) unit that arrived in this ruined city on Monday began treat flew a team of geologists to an isolated northwestern valley to investigate reports by anxious villagers of possible volcanic activity in the quake-shattered foothills, said army spokesman Maj. Gen. Shaukat Sultan.

Sultan said that if volcanic activity is found, the government was prepared to evacuate the 150,000 people who live in the Alai Valley (search).

But an official from Pakistan's meteorological department, speaking on condition of anonymity because he was not authorized to talk to the media, said there was little chance of volcanic activity as there was no recent history of eruptions in the country.

An estimated 3.3 million people have been left homeless by the quake, and despite a huge international relief effort, fears are growing that vulnerable communities could face a new disaster when winter arrives in a few weeks.

Temperatures dropped as low as 30 degrees in the mountains Tuesday, dangerous weather for those left outdoors.

Snow, landslide-blocked roads and funding shortfalls could mean more trouble as the weather worsens, the U.N. World Food Program (search) warned.

Aid workers have just five weeks to get six months worth of food supplies into the most remote areas of Pakistan before they are cut off, it said in a statement.

"It must be clear to everybody that many people could die if we do not move more quickly," said the group's director for the Middle East, Central Asia and Eastern Europe, Amir Abdulla. "We must have much more funding, much sooner, to gain as much speed as humanly possible in the face of gigantic logistics difficulties."

U.N. Secretary-General Kofi Annan has invited ministers to attend a high-level donor conference in Geneva on Wednesday to mobilize additional financial support.

Despite fresh appeals and warnings of a second wave of deaths, the United Nations said Monday it has received less than 30 percent of the $312 million it needs to help the victims. Pakistan has said rebuilding the area will cost $5 billion.

On Tuesday, the European Union proposed that member nations come up with an additional $96 million, on top of the $16.3 million already dispensed to Pakistan for emergency disaster release.

A mobile headquarters from NATO's elite response force arrived in Pakistan to help coordinate earthquake relief efforts, officials in Brussels, Belgium, said Tuesday.

Later this week, NATO was expected to send the first of up to 1,000 troops to help with the relief operation, including engineers, medics and support units for handling planes, helicopters and water purification plants.

One of the main shortcomings of the relief effort so far has been tents. As many as 800,000 people are still believed to have no shelter at all, more than two weeks after the calamity.

"If you can sum it up in one word, it's 'shelter,"' said John Moore, the head of aid in Pakistan for the Canadian International Development Agency (search), or CIDA.