SEATTLE (Reuters) - A terminal at the Port of Seattle was evacuated on Wednesday and a bomb squad was investigating a ship container that alarmed bomb-sniffing dogs, a port spokesman said. Authorities set up a 2,000-foot (610-meter) perimeter around Terminal 18, just south of downtown Seattle, port spokesman David Schaefer said. The U.S Coast Guard also established a 300-yard (274.3 meter) perimeter in the water. "There is a bomb disposal unit looking further into the container to try and figure what exactly is in the contents," said Schaefer, noting that there is no radiation from the cargo container. The container first raised suspicion when a screening using gamma ray technology about the contents' density did not match the items listed on the ships' manifest. Coast Guard Petty Officer Tara Molle said the ship's inventory list indicated the container held oily rags. Bomb-sniffing dogs detected the possible presence of explosives. All nonessential port personnel have been evacuated, Schaefer said. The Coast Guard did not know where the ship originated. The 196-acre (79-hectare) Terminal 18 is the Port of Seattle's largest container terminal and one of the largest in North America.