The Oregon Parks and Recreation Department, citing the Japanese Consulate in Portland, has confirmed on its website that a derelict dock that washed up on a local beach is debris from the 2011 tsunami in Japan.

The department also confirmed that the marine life attached to the dock is specific to Japan.

Officials in Newport, Oregon, had been trying to figure out how the 66-foot-long dock with a metal placard bearing Japanese writing wound up on Agate Beach, a mile north of Newport.

The dock was first seen floating offshore, according to the state Parks and Recreation Department.

"The origin of the object is not known, but there is no obvious evidence it crossed the ocean," the parks department said in an early statement.

The dock is 7 feet tall and 19 feet wide, made of concrete and metal but is able to float. Because of the large size, state park workers are telling residents to stay away from it.

Some immediately speculated that the dock was debris from the March 2011 tsunami since other items have washed up on Western U.S. shores after that disaster. Parks officials forwarded the placard with Japanese writing to the Japanese Consulate in Portland.

Oregon parks spokesman Chris Havel said officials tested the dock for radiation and the tests were negative. There have been concerns that tsunami debris from Japan could be contaminated by radiation because of problems at Japan's Fukushima Daiichi nuclear plant. But the National Oceanic and Atmospheric Administration has said that it is unlikely that radioactive material will make landfall in North America.

Havel said the translated placard reveals a company name, location and phone number, and officials were checking that information. He added that tires on the dock were determined to have come from a company in Japan.

CNN's Jim Kavanagh contributed to this report.