Rescuers digging through the debris of a monster US landslide found another 10 bodies Tuesday, officials said, bringing the death toll to 24 with potentially more than 170 still unaccounted for.

A day of rain hampered efforts to find survivors in the vast pile of mud and timber which crashed into the tiny town of Oso on Saturday.

"Unfortunately, we didn't find any signs of life," Snohomish County fire district chief Travis Hots told reporters, three days after the catastrophe in the northwestern US state of Washington.

He said two more bodies had been recovered, adding to the 14 corpses already brought out, while eight more were located in the debris

The number of reports of people unaccounted for remains at 176, although that could include double-counting and people who may turn up elsewhere, and so likely does not represent how many more fatalities may be found.

- 'We haven't lost hope' -

A total of 49 dwellings in the rural town were hit by the one square mile (2.5 square kilometer) wall of mud, rocks and trees, which also destroyed part of a highway some 60 miles (95 kilometers) northeast of Seattle.

Hots said the massive emergency operation was still aimed at rescuing survivors as well as recovering bodies, even though the chances of finding people alive diminish with each day.

"We haven't lost hope that there's a possibly that we can find someone," he said.

The National Guard joined local and state emergency workers after President Barack Obama declared a state of emergency for Washington state.

"I would just ask all Americans to send their thoughts and prayers to Washington state and the community of Oso and the families and friends of (the missing)," said Obama.

- Obama: 'tough situation' -

"We hope for the best, but we recognize that this is a tough situation," he added in the Netherlands, where he was attending a nuclear security summit.

The Federal Emergency Management Agency (FEMA) will help "save lives and to protect property and public health and safety, and to lessen or avert the threat of a catastrophe in Snohomish County," said the White House.

Officials insist finding survivors is still possible, even there have been no signs of life since Saturday.

"I believe in miracles and I believe people can survive these events," said emergency management chief John Pennington, adding: "They've done it before, they can do it again."

One volunteer firefighter described the landslide as "quicksand, where you could easily sink up to your armpits."

He described seeing signs of structures peeking through a dense layer of fallen timber and earth, adding that it had blocked the Stillaguamish river, which had started to flood the Darrington area.

- 'Increasingly unstable' -

"The rising river and floodwaters are making the slide areas nearest the banks increasingly unstable," the emergency worker, who did not give his name because he was not authorized to speak to the media, told AFP.

New help Tuesday included over 60 National Guardsmen, and up to 100 volunteers, officials said.

Washington state governor Jay Inslee paid tribute to all the emergency services helping the rescue effort, from local to federal.

- 'Small-town, can-do spirit' -

"There's a small town, can-do spirit here at work. It's good to have the White House as well," he said.

"We know we still have families in tremendous grief and anxiety, and we're going to do everything we can to relieve that as soon as humanly possible," he added.

The local fire chief said the rescue and recovery operation would be a long one, but pledged to try to find every last victim.

"This is going to be a very long-term event. This will be something that goes into the weeks," said Hots, adding: "We're going to do our very best to get everybody out of there."