( CNN ) -- A massive dock , possibly debris from the March 2011 tsunami that struck Japan , has washed ashore in Washington state 's Olympic National Park . A U.S. Coast Guard helicopter spotted the dock Tuesday along a remote section of the park 's coast , the Washington State Marine Debris Task Force said . Authorities were trying to reach the dock by ground Wednesday to determine whether it was tsunami debris and whether it harbors invasive species that could harm the area . The National Park Service has closed the beach in the area to the public . The Coast Guard had been searching for the dock since Friday , when a fishing vessel spotted it adrift in the ocean . Washington Gov . Christine Gregoire thanked the Coast Guard for finding the dock . `` They were out in challenging conditions looking for a needle in a haystack , and they found it , '' she said in a statement . If the dock is confirmed as tsunami debris , it would be the second to wash ashore in the Pacific Northwest this year . In June , a 66-foot-long dock turned up near Agate Beach , Oregon . In September , a 50-foot-long dock was spotted off the Hawaiian islands of Maui and Molokai . Alaska has seen much debris from the tsunami wash up on its beaches this year .
Dock lands on Olympic National Park beach in Washington state . Park Service closes beach as crews try to reach remote site . Large dock from Japan also washed up in Oregon this year .