The official death toll from Washington state's mudslide has increased to 28, with the Snohomish County medical examiner's office saying 19 victims have been positively identified. That's up from 24 dead with 18 identified on Monday.

Workers are trying to improve the flow of the Stillaguamish River through the landslide at Oso to reduce flooding as they continue the grim task of recovering bodies.

A statement issued by the coroner's office also said the remains of 22 victims have now been positively identified, up from 19 earlier in the day. The number of people still listed as missing was put at 22 on Monday.

The latest name added to the list is 58-year-old Brandy L. Ward of Arlington. Like the rest she was killed by blunt force injuries in the March 22 slide.

Estimated financial losses from the deadly mudslidehave reached $10 million US, Gov. Jay Inslee said Monday in a letter asking the federal government for a major disaster declaration.

In seeking additional federal help following one of the deadliest landslides in U.S. history, Inslee said about 30 families need assistance with housing, along with personal and household goods. The estimated losses include nearly $7 million in structures and more than $3 million in their contents, Inslee's letter said.

Officials have given no estimate of how much longer they might press on before giving up the search for additional remains. The governor's office said that decision would eventually be made by the joint incident command, consisting of on-site leaders of the various local, state and federal agencies involved in the operation.

22 people still missing

The remains of three additional victims were found Monday, but they have not yet been included in the medical examiner's official numbers, Snohomish County Executive Director Gary Haakenson told reporters at a Monday evening briefing.

The county sheriff's office released a list of 22 people believed missing following the March 22 slide that destroyed a rural mountainside community northeast of Seattle. That's down from the 30 people officials previously considered missing.

'We want to do all we can to find them and put some closure in place for their families.'- Gary Haakenson, Snohomish County executive director

"There's been an exhaustive effort by the detectives to narrow the list down to one that they feel comfortable releasing," Haakenson said.

"These are 22 people whose loved ones are grieving," he said. "We want to do all we can to find them and put some closure in place for their families."

He said there could be some overlap between the list of missing and the handful of victims who have not been positively identified by the medical examiner.

Steve Harris, a division supervisor for the search effort, said Monday that search teams have been learning more about the force of the slide, helping them better locate victims in a debris field that is about 21 metres deep in places.

"There's a tremendous amount of force and energy behind this," Harris said of the slide.

Harris said search dogs are the primary tool for finding victims, and searchers are finding human remains four to six times per day. Sometimes crews only find partial remains, which makes the identification process harder.

Inslee's request Monday also seeks federal help with funeral expenses, and mental health care programs for survivors, volunteers, community members and first responders.

He also is asking for access to disaster housing, disaster grants, disaster-related unemployment insurance and crisis counselling programs for those in Snohomish County and for the Stillaguamish, Sauk-Suiattle and Tulalip Indian tribes.

'Hallowed ground'

With the realization that some remains may never be recovered from a mound of mud and debris up to 25 metres deep has come growing sentiment that the site should ultimately be turned into a memorial or park.

Ruth Hargrave, 67, whose neighbours are among the dead and missing, said she could not imagine rebuilding the beloved riverside vacation house that was in the path of the slide.

"Oh my God, no!" she said. "And not because of the fear of more slides. But all of that death and destruction."

Hargrave said the stricken community, 1.3 square kilometres of which lies under the mud, should be treated as "hallowed ground." Her view is shared by many who live in the surrounding area.

"There ought to be a marker put up there honouring the people who died," said Jan Kittleson, 59, a truck driver from Darrington, 16 kilometres to the east.

"The river will cut its way through there the way it always has."

Daniel Miller, a geologist and author of a 1999 study for the U.S. Army Corps of Engineers warning of the potential for a "large catastrophic failure" in the vicinity of the collapsed hillside, said additional slides in the area were likely.

"I don't think anybody should be living there," he said. "It would be okay to do something like a park, but I don't think there should be houses down there."

Seattle football, soccer teams visit

Meanwhile, a dozen members of the Seattle Seahawks football team and Seattle Sounders FC soccer team visited Monday with more than 300 children, parents and area residents at the Darrington Community Centre.

MLS Washington Mudslide Sounders Soccer

Seattle Sounders' Micheal Azira, right, with Sounders' Kenny Cooper, left, joined other players from their team and the NFL football Seattle Seahawks in a visit to Darrington, Wash., to lend support to the town. (Ted S. Warren/The Associated Press)

Players said they signed autographs, tossed footballs and kicked soccer balls in an effort to bring some smiles to an area hit by tragedy.

"To be able to offer a little bit of a release or a distraction from what's going on, I mean that's all you can do," Seahawks linebacker Malcolm Smith said.

Sounders forward Kenny Cooper said he played pickup soccer with the kids.

One child, 10-year-old Jacob Spelman, wore an autographed bright green hat commemorating the Seahawks' Super Bowl victory as he spoke to reporters after the visit.

"I just feel like they care and that they would like it if we felt better and they came to help us," he said.

With files from Reuters