A large derelict dock that washed ashore this week on Agate Beach near Newport had a plaque with Japanese writing is on it, and on Wednesday, officials confirmed it was torn away from Japan by the March 2011 tsunami and floated across the Pacific Ocean to Oregon.

The large, heavy dock is a concrete and metal pontoon that measures 66 feet long, 7 feet high and 19 feet wide. State officials said it "is clearly designed to float."

A metal placard bearing Japanese writing was found attached to the dock that washed ashore early Tuesday morning, a mile north of Newport. The placard was forwarded to the Japanese consulate in Portland for confirmation.

State Parks and Recreation Department officials said Monday, "Because of its size and the chance it could continue to settle or be moved by wave action, state park staff are posting warning tape and signs instructing the public to stay off the structure."

State park staff, in cooperation with other authorities, are discussing options to remove the object from the beach. Agate Beach remains open, but visitors are urged to stay off the dock.

Shortly after the dock made landfall, it was checked for radiation and was found to be negative.

Scientists at the Hatfield Marine Science Center in Newport have verified that there is evidence of marine life specific to Japan attached to the dock.

There is some concern about potential invasive species exposure. OPRD is working with Oregon Department of Fish and Wildlife to contain this threat.

OPRD officials said Wednesday they are still developing disposal options. Two possibilities are salvage or demolition; both are being evaluated

Sen. Ron Wyden, among others, have raised concerns and urged preparation work for possible large amounts of tsunami debris -- perhaps some hazardous -- to reach U.S. shores on ocean currents in coming months and years.

Fast-moving debris from the tsunami has already arrived on the shores of North America. It includes a soccer ball and a shipping container holding a Harley-Davidson motorcycle with Japanese license plates.

The bulk of the debris is not expected until winter.

Wyden issued the following statement Wednesday after confirmation the dock indeed was tsunami debris:

?The huge dock that washed ashore in Agate Beach is clear evidence that debris from last year?s tsunami in Japan is reaching the Oregon Coast much sooner than anyone predicted. This massive dock, which crossed the Pacific Ocean undetected in 15 months, may be the vanguard of more debris to come.

"With the strong possibility that more debris could pose a significant threat to shipping lanes and fishing grounds, I encourage the National Oceanic and Atmospheric Administration to redouble its efforts in tracking debris generated by the Japanese earthquake and to work closely with other federal, state and local agencies to inform the public how best to report suspected debris.