Kayakers surveying Washington state's most remote beaches for debris from last year's Japanese tsunami say they believe they have found part of a house, along with pieces of a washing machine, laundry hamper and child's toilet bowl.

Three kayakers with the Ikkatsu Project wrote in a report this week that they found the remnants on June 12 as they worked their way up a beach near the northwestern tip of the Olympic Peninsula on the Makah Indian Reservation.

They discovered a lumber pile mixed in with driftwood and seaweed. The lumber's dimensions were metric, and some of it was stamped with a serial number they traced to a mill in Osaka — the Diawa Pallet Housou Co., the kayakers wrote.

Some of pieces were nailed together, kayaker Ken Campbell said Tuesday.

In the same area, other household items were also recovered, including a glass bottle of cherry-flavored cough syrup and a red container of kerosene with Japanese writing. Kerosene is widely used to heat homes in Japan.

It was exciting to find what appeared to be the remnants of a home, Campbell said.

But he added: "It was sobering, especially when you're smelling somebody else's cough syrup. Somebody lived here and it doesn't look like a house anymore. I was not prepared to find something like that."

Curtis Ebbesmeyer, a Seattle oceanographer who is on the expedition's advisory board, said it is too soon to confirm whether the debris was from a Japanese home.

"It's like an archaeological dig," he said Tuesday. "It's a bunch of things that could be construed as a house."

If so, it might be the first case of a Japanese home floating 5,000 miles across the Pacific Ocean after the devastating earthquake and tsunami of March 11, 2011.

Meanwhile, the barnacle-covered boat that washed up on a southwest Washington beach Friday has been traced to its owner in Japan, who says he lost it during the tsunami, according to a staffer with the Japanese consulate-general in Seattle.

U.S. officials provided the Japanese government with what appeared to be a registration number on the boat.

The former owner is from the Tohoku region, on the northeastern portion of Honshu, Japan's largest island, which was hard hit by the tsunami, according to Travis Doty, a staffer with the consulate-general.

Doty did not have information about the owner's occupation, or how the boat was used. But he said the owner does not intend to retake possession of the craft and does not object to its disposal.

The boat, an estimated 20 feet long, was found beached at Cape Disappointment State Park.

The boat was cleaned of barnacles and other sea life by a team of state officials, who filled some 20 trash bags with it. No invasive species were found, according to the state Department of Ecology. State costs for the boat removal and cleanup are still being tallied.

According to the National Oceanic and Atmospheric Administration, as of Monday there have been 404 total reports of potential tsunami debris along the West Coast from California to Alaska and in the ocean — 40 in the last week. Nine, including the boat, are confirmed tsunami debris.

The arrival of debris from the tsunami has worried officials on the West Coast and in Alaska. They say it will be expensive to clean and could carry invasive species — a serious threat to the fishing industry. On Monday, Gov. Chris Gregoire called for federal help dealing with the debris.

The kayakers — Campbell, Steve Weileman and Jason Goldstein — are longtime friends who had wanted to kayak the Olympic Peninsula's Pacific Coast and decided to survey the beaches along the way.

They aren't scientists, but they contacted Ebbesmeyer and others to learn surveying methods that would be useful to researchers, Campbell said.

They named their expedition the Ikkatsu Project, after a Japanese word for "unity," and they are dividing the trip into three segments, the last of which will be completed in August.

The team's work will help establish a baseline for measuring how much more tsunami debris arrives this fall and winter, Ebbesmeyer said.

The kayakers said they didn't have the resources to search through the entire lumber and debris pile, and Campbell said they didn't find anything with a name or address — though in retrospect, they could have looked harder.

"It was my first time finding a house; what can I say," Campbell said. "Next time, I'll be much more thorough."