Rescue crews continued their frantic search Sunday at a Himalayan military outpost near the Indian border where a massive avalanche buried up to 139 people, most of them Pakistani soldiers.

A blanket of rock and snow covering one square kilometer -- about the size of a large city block -- slid over the base on the Siachen glacier early Saturday morning, entombing it under 70 feet of snow.

The Siachen Glacier, known as the world's highest battleground, is 6,300 meters (20,670 feet) high and spans 77 kilometers (47 miles) across the Line of Control that separates India- and Pakistan-controlled Kashmir.

A press release Sunday from the Pakistani military indicated that 139 people were believed trapped in the avalanche -- a figure that is slightly higher than previously reported.

None of the searches thus far has led to the discovery of any survivors, and poor weather has hampered such efforts.

"It's a very massive scale slide," Maj. Gen. Athar Abbas said Saturday. "They are under the slide, but we haven't lost hope. The rescue work is on, and we are keeping our fingers crossed."

Crews flew in heavy machinery from neighboring Rawalpindi. Sniffer dogs and troops using bulldozers worked the ground.

Abbas said the military had not been able to establish contact with anyone inside the base since the avalanche.

Army Chief of Staff Gen. Ashfaq Parvez Kayani visited Siachen on Sunday, noting Pakistan's military is mobilizing all possible resources for the search effort. He said the army "has always risen to the occasion and will come through this challenge as well."

It was the first such disaster at the mountain headquarters in its two decades of existence, the military said.

India, too, maintains a base on its side of the glacier in the disputed Kashmir region.

Kashmir has been a source of bitter dispute between India and Pakistan since their independence in 1947.

Under terms that the two countries agreed to at the time, Kashmir's rulers could either opt to merge with India or Pakistan or remain independent.

One part sided with Pakistan.

The ruler of the other part sided with India, where most people are Hindu. That caused controversy among the region's Muslim majority. Many of them wanted to align with Pakistan, where Islam is the dominant religion.

Since then, the Kashmir issue has been the leading cause of conflict and two of three wars between the two countries.

The Line of Control was formally established in 1972.

But there have been routine accusations that both sides fire across the line -- accusations both have denied.

In 1984, India occupied key portions of the glacier. Three years later, the two sides fought bitterly over Siachen.

Both maintain year-round military camps on their sides of the disputed mountainous region.

In February, two avalanches swept over military camps in the Indian-controlled side of Kashmir, killing at least 11 soldiers.

The avalanches hit two army camps in the health resort of Sonamarg and at Dawar, a town close to the Line of Control.

In January, another avalanche hit a joint patrol of the Indian army and border security forces in the Keran area, killing seven.

Winter in Kashmir this season is harsher than previous years, with several snowfalls and sharp dips in temperatures.