Thousands of rescuers used heavy machinery and shovels Thursday to clear mud and search for survivors after huge landslides and flooding killed at least 39 people in South Korea.

Three others were reported missing in the wake of the massive rains that have pounded Seoul and surrounding areas since Tuesday. It was the heaviest rainfall in South Korea this year.

Among the dead were 10 college students who were engulfed by a landslide while sleeping in a resort cabin in Chuncheon, north of Seoul. The students from Inha University in Incheon, just west of Seoul, were volunteering at a local elementary school.

Nearly 700 firefighters and others rushed to rescue those believed trapped and pull the dead from the mud and wreckage in Chuncheon, but they stopped their work on Wednesday evening after it became apparent no one else was missing, Chuncheon fire officials said. The landslide injured 24 others and destroyed several buildings.

At least 15 people died when mud crashed through homes at the foot of a mountain in southern Seoul. The National Emergency Management Agency reported 11 more deaths due to a stream flooding and landslides in towns near Seoul.

On Thursday, about 7,000 firefighters, soldiers, police officers and others mobilized to try to find any survivors and clean walls of mud after the flash floods that hit parts of Seoul, emergency official Kim Jae-un said.

Fast-moving, muddy water filled the streets in Seoul on Wednesday, sending residents scrambling to the roofs of their partially submerged cars.

Water filled some subway stations and spewed from sewers. TV images showed people in one flooded subway station using shovels, brooms and a wooden board in an effort to keep more rain from coming in.

Footage showed officials rescuing hikers stranded on mountainsides. People plodded down streets covered with knee-deep water, many barefoot, their pants rolled up. In Seoul's center, cars were restricted from entering the lower part of a submerged two-level bridge.

About 17 inches (440 millimeters) of rain fell on Seoul and more than 13 inches (340 millimeters) on Chuncheon on Tuesday and Wednesday, about 15 times more than the average two-day rainfall at this time of year, according to the state-run Korea Meteorological Administration.

Weather officials said another 10 inches (254 millimeters) could fall in northern South Korea, including Seoul, through Friday. (AP)