Sightseers flocking to see a tsunami-wrecked dock washed up on a US beach were urged Friday to reflect on the "tragedy" of last year's killer quake and tidal wave in Japan.

Local authorities in Oregon, where the 66-foot (20-meter) floating dock made landfall Tuesday after a 5,500 mile, 15-month trip across the Pacific, said they had not yet decided how to dispose of it.

But they issued advice to people coming to look at the huge wreck on Agate beach, near the town of Newport some 100 miles (160 kilometers) southwest of Portland.

People should visit at low tide and be prepared for traffic congestion, it said, while also warning: "When on the beach, keep a close eye on each other. The surf here can be surprisingly fierce."

"Stay off the dock. Look, touch, reflect on the original tragedy that brought this visitor to Oregon's shores, but do not compound the sadness of that day by suffering an injury," it said.

The Oregon Parks and Recreation Department, which issued the advice, said it was seeking bids for the dock's removal, saying it had not yet decided whether the wreck should be demolished on site, or towed to nearby Newport.

Japanese officials confirmed that the dock -- 66 feet long, 19 feet wide and 7 feet tall -- came from the port of Misawa, in Aomori prefecture in the northern part of Japan. A Japanese-language metal plaque was dated June 2008.

The wreck has been checked for radioactivity -- the killer earthquake and tsunami triggered a disaster at the Fukushima nuclear plant on Japan's east coast -- but proved negative, said the OPRD spokesman.

On Thursday a team of about a dozen workers stripped seaweed, barnacles and other marine life from the dock, and sterilized it with flame torches, to guard against "invasive species" from Japan which could harm the local ecosystem.

Various debris from the Japanese tsunami have begun washing up on the US and Canadian west coast, and experts predict a surge of flotsam in the coming months.