The object has not been relocated or confirmed since it was initially reported Friday by fishermen, Keeley Belva, a spokeswoman with the National Oceanic and Atmospheric Administration, said Monday.
Fishermen aboard the vessel Lady Nancy reported seeing a large object floating off the coast, about 16 nautical miles northwest of Grays Harbor. The object is similar to a large dock that beached in Oregon over the summer, officials said.
The Coast Guard has been broadcasting alerts to mariners about the floating debris spotted last week, and helicopter crews have also conducted five searches, covering about 320 square miles, in search of the object.
"It doesn't pose a danger right now to anyone," said Coast Guard spokesman Robert Lanier, adding that the goal is to locate it, attach a data marker and track exactly where it goes to agencies that can deal with it responsibly.
The Coast Guard is working with NOAA, state agencies and the Quinault Indian nation to track the object.
Terry Egan, the tsunami marine debris lead for Washington state who is with the Washington Emergency Management Division, said modeling estimates the dock could likely reach landfall near the Quinault Indian Nation reservation or on Olympic National Park land.
The object sits low in the water and may be difficult to spot in rough waters, Egan said.
"My preferred response is to get it at sea, get a beacon on it and get a tugboat to tow it to the nearest port where we can deal with it, while safeguarding any transfer of invasive species," he said.
Egan said a scientist studying tsunami debris from Japan believes that the dock floating off Washington's coast may be one of four pieces from the fishing port of Misawa. One of those turned up at Newport, Ore., in June.
Staff from Olympic National Park plan to patrol the area near Ruby Beach on Tuesday to see if the object has washed ashore, said park spokeswoman Rainey McKenna.
Members of the Quinault tribe drove along the coast and scanned the beach from a high spot but did not find anything Monday, said John Preston, the tribe's emergency management director.
"We're really concerned about invasive species," he said.
Meanwhile, U.S. Sen. Maria Cantwell has pushed through new legislation intended to speed up federal response to marine debris cleanup, the Daily World of Aberdeen reported Sunday (http://is.gd/KPHoIX ).
That legislation was added as an amendment to the Coast Guard authorization bill, HR 2838, and awaits approval by President Barack Obama, the newspaper reported. It directs NOAA's administrator to form a task force to come up with a tsunami debris cleanup plan.
"The plan would make tsunami debris cleanup more effective by coordinating and directing all debris removal in Washington state and across the West Coast," Cantwell said in a statement.
NOAA's Marine Debris Program has been leading efforts to collect data, assess debris and reduce possible impacts to coastal communities and natural resources.
The Japanese government estimated that the March 11, 2011, tsunami swept about 5 million tons of debris into the Pacific Ocean. Most of that sank immediately, while 1.5 million tons were dispersed across the North Pacific Ocean.
NOAA estimates the bulk of what is coming either has arrived or will in the next year or so but that's a rough guess.
NOAA has received about 1,400 debris reports in the past year, including bottles and buoys. Of those reports, 17 have been confirmed as definite tsunami debris, including a 20-foot boat, pieces of which were recovered earlier this month in Hawaii.