A huge floating dock has washed up on an Oregon beach, possibly having drifted across the Pacific after last year\'s killer tsunami in Japan, officials and locals said Wednesday. The 66-foot (20-meter) long rectangular structure, made of concrete and metal, was spotted floating off the coast on Monday, and then washed in with the high tide on Agate beach, 100 miles (160 kilometers) southwest of Portland. Speculation that it may be from the tsunami has been fueled by Japanese writing and markings on various parts of the seaweed-covered dock, including \"Shibata, Japan\" on tires, apparently designed to make it buoyant. \"We don\'t know where it\'s from, we don\'t know if it\'s from Japan or not. But we have to eliminate those possibilities as we go forward,\" said spokesman Chris Havel of the Oregon State Parks Department. Photos of the structure, and at least one Japanese-language placard attached to it, have been sent to the local Japanese consulate, he told KATU 2 television news. Various debris from the March 11, 2011 tsunami have begun washing up on the US and Canadian west coast, and experts predict a surge of flotsam in the coming months, having drifted the 5,500 miles from Japan. Kirk Tite, visiting the Oregon beach with his young son Trevor, said: \"It\'s kind of scary seeing this wash up here, because we all surf.\" \"If this crossed the Pacific Ocean and it\'s this big, that means that just about anything of our worst nightmares could cross the Pacific Ocean. So we\'re kind of frightened of what\'s to come,\" he told KATU 2. The broadcaster said it had traced a phone number on a Japanese placard to a business located in Tokyo, called Zeniya Marine Services Company, Ltd., which builds docks and other floating marine structures. The dock has been checked for radioactivity -- the killer earthquake and tsunami triggered a disaster at the Fukushima nuclear plant on Japan\'s east coast -- but had proved negative, it reported. Trevor Tite, examining shellfish attached to the side of the dock, was bemused. \"I just think it\'s kind of weird that it could have come over from Japan... the tsunami, that happened quite a while ago.\" In early April, the US Coast Guard sunk a deserted Japanese trawler that had appeared off the coast of Alaska more than a year after being set adrift by the tsunami. In the same month, a Japanese schoolboy was told he was getting his football back, after it was spotted by an observant beachcomber on Middleton Island in the Gulf of Alaska.