Toxic gases Tuesday hampered the search for 138 people buried by an avalanche at a high-altitude Pakistan army camp, as teams from the United States and Norway arrived at the site to help operations.

A huge wall of snow crashed into the remote Siachen Glacier base high in the mountains in disputed Kashmir more than a week ago, smothering an area of one square kilometre (a third of a square mile).

Rescuers have dug tunnels in the hard mass of snow and ice to try to reach the buried soldiers and civilians at the Gayari base, but toxic gases have built up inside one of them, the military said in a statement.

A rise in the temperature has increased the risk of further snow slides, the statement said, forcing workers on the site to take extra precautions.

Specialist teams from Norway and the United States arrived at Gayari, while Swiss and German teams have returned home after helping the efforts.

Search teams are looking for the trapped soldiers and civilians at six different points on the site, around 4,000 metres (13,000 feet) up in the mountains.

More than 450 rescuers are working at the site near the de facto border with India in the militarised region of Kashmir, though experts have said there is virtually no chance of finding any survivors.

Kashmir has been the cause of two wars between India and Pakistan and the nuclear-armed rivals fought over Siachen in 1987, though guns on the glacier have largely fallen silent since a peace process began in 2004.