Hundreds of volunteers take part in a rescue work at the site of the collapsed 10-story apartment building in Islamabad, Saturday

Relief workers in Pakistan are scrambling to locate and reach survivors after Saturday's devastating earthquake. Rescue teams say landslides and rugged terrain have kept them from reaching parts of the most severely affected regions. With nearly 20,000 people killed, rescue workers say removing and burying the dead is another daunting task.

Sigurd Hanson, the country director for the U.S.-based aid agency, World Vision, says key access roads remain blocked by landslides. He says it is still not clear how soon aid workers will be able to reach many of the quake's victims and assess the extent of the damage in those areas.

Mr. Hanson says, in addition to shelter and medical supplies, many of the hardest hit areas need help tending the injured and burying the dead.

"Dead bodies are everywhere. Hospitals are completely full. Wounded are just
lying around on the compound," Mr. Hanson says. "Unfortunately, when the earthquake initially hit,
so many children are in school, so hundreds of school children died."

Pakistani rescue workers remove a body from rubble of 10-story apartment building that collapsed in Islamabad, Pakistan

Pakistani officials have also acknowledged that the country was unprepared for
a crisis of this magnitude, and desperately needs modern rescue equipment.

Even in the country's capital, Islamabad, where a 10-story building collapsed
Saturday, a local rescue worker said there is enough manpower, but, without
proper equipment, digging for survivors is slow and frustrating work.

"People cannot do much with their hands, and with not having the right kind of
equipment. That is the problem," the rescue worker says.

Two days after the building caved in, authorities say more than 50 survivors
may remain beneath the mountain of broken cement.

Western countries are quickly stepping up to try and fill the gap. Several
teams with equipment have already come from countries offering aid, including the United States, Thailand, Japan and China.