A North Korean spy ship that sank in the East China Sea in 2001 may also have ferried agents to and from Japan, officials of a joint police-coast guard team analyzing the salvaged ship said Friday.

The officials said they had discovered a map of the southeastern coast of Kagoshima Prefecture's Satsuma Peninsula inside the retrieved vessel.

This "makes it difficult to disregard the possibility that North Korean agents had gone in and out of the country" using the ship, an official said.