One of two British explorer ships that vanished in the Arctic nearly 170 years ago during a search for the fabled Northwest Passage has been found, Canada's prime minister announced on Tuesday in a discovery that could unlock one of history's biggest mysteries and swell Canadian pride.

Last seen in the 1840s while under the command of Rear Adm. Sir John Franklin, HMS Erebus and HMS Terror have long been among the most sought-after prizes in marine archaeology and the subject of songs, poems and novels.

Prime Minister Stephen Harper's office said the well-preserved wreck of one of the vessels was found Sunday with the help of a remotely operated underwater vehicle. It was near King William Island, about 1,200 miles northwest of Toronto.